Relevance of TSH evaluation in elderly in-patients with non-thyroidal illness.

BACKGROUND: Non-thyroidal illness (NTI) is frequent in hospitalized patients. Its recovery is characterized by a raise in TSH levels. However, the clinical significance of high TSH levels at admission in hospitalized elderly patients with NTI remains uncertain. AIM: To explore the relevance of baseline TSH evaluation in hospitalized elderly patients with NTI. METHODS: We examined the participants with NTI (n = 123) from our previous study (Sforza, 2017). NTI was defined as: low T3 (< 80 ng/dL) and normal or low total T4 in the presence of TSH values between 0.1 and 6.0 mU/L. Thyroid function tests were performed on day 1 and day 8 of the hospital stay. Positive TSH changes (+ ΔTSH) were considered when the day-8 TSH value increased more than the reference change value for TSH (+ 78%). Multiple logistic regression was used to evaluate the independent association of baseline TSH, sex, clinical comorbidities (by ACE-27) and medications with + ΔTSH. RESULTS: Out of 123 patients (77 ± 8 years, 52% female), 34 showed a + ΔTSH. These patients had a lower TSH at admission (p < 0.001) and intra-hospital mortality (p = 0.003) than the others. In multiple logistic regression, TSH > 2.11 mU/L at baseline was associated with reduced odds to show + ΔTSH [odds ratio (95 CI) 0.29 (0.11-0.75); p = 0.011] in a model adjusted by age, sex and ACE-27. DISCUSSION: Inappropriately higher TSH levels at admission in hospitalized elderly patients were associated with a reduced ability to raise their TSH levels later on. The present results confront the idea that TSH levels at admission are irrelevant in this clinical context.

Hypothyroidism in hospitalized elderly patients: a sign of worse prognosis.

PURPOSE: Overt hypothyroidism has adverse clinical consequences and might worsen prognosis in critically ill elderly patients. However, the difficult interpretation of thyroid function tests (TFT) due to non-thyroidal illness (NTI) has led to discouragement of screening for thyroid dysfunction. Our aim was to determine the prevalence of TFT compatible with hypothyroidism and to study its influence on mortality among hospitalized elderly patients. METHODS: In this prospective study we consecutively included all patients ≥60 years admitted by the Internal Medicine Department to the hospital ward (n = 451) of the Cesar Milstein Hospital in Buenos Aires, Argentina. TFT were done on day 1 and 8. Thyroid function categories were defined as overt and subclinical hypothyroidism, overt and subclinical hyperthyroidism, euthyroidism and NTI. Stage of chronic kidney disease (CKD), Adult Comorbidity Evaluation (ACE)-27, and intra-hospital mortality were recorded. The association between mortality and TFT categories was studied by Cox regression. RESULTS: Out of 451 patients (77.0 ± 7.9 years, 54% females) 76% were categorized as NTI, 4% as overt hypothyroid, 10% as subclinical hypothyroid, 1% as subclinical hyperthyroid and 9% as euthyroid. Overt hypothyroid patients showed significantly higher mortality than the rest of the groups (25%, p < 0.05) while ACE-27 was similar among all of them (p = 0.658). In addition, patients within the overt hypothyroid category showed a higher mortality rate than NTI in a model adjusted by Stage 5-CKD, ACE-27, sex and age [HR 3.1 (1.14-8.41), p < 0.026]. CONCLUSION: Overt hypothyroidism during hospitalization was associated with elevated mortality. Further studies would reveal if TFT alterations compatible with hypothyroidism should be diagnosed/treated in hospitalized elderly patients.

Correlación entre osteocalcina, insulinorresistencia, insulinosensibilidad y metabolismo de la glucosa en adultos mayores con síndrome metabólico / Correlation between Osteocalcin, Insulin Resistance, Insulin Sensitivity and Carbohydrate Metabolism in an Elderly Population with Metabolic Syndrome

Introducción: Recientemente han surgido nuevas evidencias que relacionan el metabolismo óseo con el energético. La osteocalcina es una proteína de la matriz ósea no colágena, sintetizada por los osteoblastos que modula localmente la mineralización ósea, tradicionalmente usada como marcador de formación ósea. Se ha demostrado tanto en modelos "in vitro" como en animales de experimentación que la osteocalcina tiene acción hormonal. Esta proteína tiene la propiedad de regular la insulinosensibilidad, la insulinosecreción y la proliferación de las células beta pancreáticas. Objetivo: Evaluar la existencia de correlación entre los niveles de osteocalcina sérica y marcadores de insulinorresistencia (IR) e insulinosensibilidad en una población de adultos mayores con síndrome metabólico. Material y métodos: En nuestro estudio prospectivo se incluyeron 88 pacientes (68 % mujeres, 32 % hombres, media de edad 73 ± 6 y 74 ± 6 años respectivamente) que concurrieron a los consultorios externos del servicio de Endocrinología y Metabolismo del hospital Dr. César Milstein. Todos cumplían con los criterios diagnósticos de síndrome metabólico del año 2009 de la Federación Internacional de Diabetes (IDF). Se midieron: osteocalcina sérica, hemoglobina glicosilada (HbA1c), HDL y triglicéridos (TG). Se calcularon QUICKI (Quantitative Insulin Sensivity Check Index) y el índice TG/HDL. Resultados: Los niveles de osteocalcina sérica se asociaron positivamente con HDL (r = 0,213, p = 0,05) y QUICKI (r = 0,212, p = 0,05) e inversamente con TG (r = -0,218, p < 0,05), con el índice TG/HDL (r = -0,217, p < 0,05) y con HbA1c (r = -0,253, p < 0,05). Conclusiones: Nuestro estudio mostró que en adultos mayores con sindrome metabólico, los niveles de osteocalcina reducidos se asociaron con un aumento en los índices de insulinorresistencia, una disminución de los de insulinosensibilidad y un peor control metabólico. Rev Argent Endocrinol Metab 52:8-13, 2015 Los autores no poseen conflictos de interés.

Introduction: In recent years there has been increasing evidence about the relationship between bone and energy metabolism. Osteocalcin is a non-collagenous bone matrix protein synthesized by osteoblasts that locally modulates bone mineralization and is traditionally used as a bone formation marker. Osteocalcin has been shown to have hormonal actions both in in vitro models and in experimental animals. This hormone has the property of regulating insulin secretion and insulin sensitivity as well as beta pancreatic cell proliferation. Aim: To evaluate the existence of correlation between serum osteocalcin levels, insulin resistance and insulin sensitivity markers in an elderly population with metabolic syndrome. Material and methods: Eighty-eight elderly patients were included in our prospective study (68 % women, mean age 73 ± 6 ; 32 % men, mean age 74 ± 6). They attended the outpatient Endocrinology and Metabo­lism service at Dr. César Milstein Hospital and met the International Diabetes Federation (IDF) criteria of metabolic syndrome. Serum Osteocalcin, Glycated haemoglobin (HbA1c), HDL and Triglycerides (TG) were measured. QUICKI and TG/HDL index were calculated. Results: Serum osteocalcin levels were positively associated with HDL (r = 0.213, p = 0.05) and QUICKI (r = 0.212, p = 0.05), and inversely associated with TG (r = -0.218, p < 0.05), TG/HDL index (r = -0.217, p < 0.05) and HbA1c (r = -0.253, p < 0.05). Conclusions: Our study showed that in elderly patients with metabolic syndrome, reduced osteocalcin levels were associated with increased insulin sensitivity, decreased insulin resistance indexes and impaired metabolic control. Rev Argent Endocrinol Metab 52:8-13, 2015 No financial conflicts of interest exist.

Correlación entre osteocalcina, insulinorresistencia, insulinosensibilidad y metabolismo de la glucosa en adultos mayores con síndrome metabólico / Correlation between Osteocalcin, Insulin Resistance, Insulin Sensitivity and Carbohydrate Metabolism in an Elderly Population with Metabolic Syndrome

Introducción: Recientemente han surgido nuevas evidencias que relacionan el metabolismo óseo con el energético. La osteocalcina es una proteína de la matriz ósea no colágena, sintetizada por los osteoblastos que modula localmente la mineralización ósea, tradicionalmente usada como marcador de formación ósea. Se ha demostrado tanto en modelos "in vitro" como en animales de experimentación que la osteocalcina tiene acción hormonal. Esta proteína tiene la propiedad de regular la insulinosensibilidad, la insulinosecreción y la proliferación de las células beta pancreáticas. Objetivo: Evaluar la existencia de correlación entre los niveles de osteocalcina sérica y marcadores de insulinorresistencia (IR) e insulinosensibilidad en una población de adultos mayores con síndrome metabólico. Material y métodos: En nuestro estudio prospectivo se incluyeron 88 pacientes (68 % mujeres, 32 % hombres, media de edad 73 ± 6 y 74 ± 6 años respectivamente) que concurrieron a los consultorios externos del servicio de Endocrinología y Metabolismo del hospital Dr. César Milstein. Todos cumplían con los criterios diagnósticos de síndrome metabólico del año 2009 de la Federación Internacional de Diabetes (IDF). Se midieron: osteocalcina sérica, hemoglobina glicosilada (HbA1c), HDL y triglicéridos (TG). Se calcularon QUICKI (Quantitative Insulin Sensivity Check Index) y el índice TG/HDL. Resultados: Los niveles de osteocalcina sérica se asociaron positivamente con HDL (r = 0,213, p = 0,05) y QUICKI (r = 0,212, p = 0,05) e inversamente con TG (r = -0,218, p < 0,05), con el índice TG/HDL (r = -0,217, p < 0,05) y con HbA1c (r = -0,253, p < 0,05). Conclusiones: Nuestro estudio mostró que en adultos mayores con sindrome metabólico, los niveles de osteocalcina reducidos se asociaron con un aumento en los índices de insulinorresistencia, una disminución de los de insulinosensibilidad y un peor control metabólico. Rev Argent Endocrinol Metab 52:8-13, 2015 Los autores no poseen conflictos de interés.(AU)

Introduction: In recent years there has been increasing evidence about the relationship between bone and energy metabolism. Osteocalcin is a non-collagenous bone matrix protein synthesized by osteoblasts that locally modulates bone mineralization and is traditionally used as a bone formation marker. Osteocalcin has been shown to have hormonal actions both in in vitro models and in experimental animals. This hormone has the property of regulating insulin secretion and insulin sensitivity as well as beta pancreatic cell proliferation. Aim: To evaluate the existence of correlation between serum osteocalcin levels, insulin resistance and insulin sensitivity markers in an elderly population with metabolic syndrome. Material and methods: Eighty-eight elderly patients were included in our prospective study (68 % women, mean age 73 ± 6 ; 32 % men, mean age 74 ± 6). They attended the outpatient Endocrinology and Metabo¡lism service at Dr. César Milstein Hospital and met the International Diabetes Federation (IDF) criteria of metabolic syndrome. Serum Osteocalcin, Glycated haemoglobin (HbA1c), HDL and Triglycerides (TG) were measured. QUICKI and TG/HDL index were calculated. Results: Serum osteocalcin levels were positively associated with HDL (r = 0.213, p = 0.05) and QUICKI (r = 0.212, p = 0.05), and inversely associated with TG (r = -0.218, p < 0.05), TG/HDL index (r = -0.217, p < 0.05) and HbA1c (r = -0.253, p < 0.05). Conclusions: Our study showed that in elderly patients with metabolic syndrome, reduced osteocalcin levels were associated with increased insulin sensitivity, decreased insulin resistance indexes and impaired metabolic control. Rev Argent Endocrinol Metab 52:8-13, 2015 No financial conflicts of interest exist.(AU)

Particularidades del síndrome metabólico en una subpoblación de adultos mayores / Particularities of metabolic syndrome in an elderly subpopulation

Introducción: El síndrome metabólico (SM) se define por un conjunto de alteraciones clínicas que aumentan el riesgo de enfermedad cardiovascular. Diferentes organizaciones internacionales de salud han ajustado progresivamente los criterios que definen al SM, con el consiguiente aumento del diagnóstico del mismo. Sin embargo, ninguno de los parámetros considerados se han adaptado a la edad ni se han tomado en cuenta las modificaciones antropométricas y metabólicas características del envejecimiento. Objetivo: Caracterizar al SM en una población de adultos mayores y evaluar si existen diferencias de género. Materiales y métodos: Se realizó un estudio prospectivo en pacientes que consultaron al Servicio de Endocrinología de la U. A. Dr. César Milstein. El 68,8 % fueron mujeres y la edad de la población fue 73 ± 6 años. Para el diagnóstico de SM se utilizaron los criterios del Joint Interim Statement de 2009. Recabamos información sobre antecedentes, medicación y se realizaron análisis de laboratorio. Se midió índice cintura/talla (ICT). Se calculó media ± desvío estándar (DS) y proporciones. Para establecer comparaciones entre varones y mujeres se utilizó Test de Student y test de Chi2. Resultados: En una muestra de 77 pacientes, 42,9 % cumplió con 3 componentes de SM, 33,8 % con 4 y 23,4 % con 5, con distribución similar en hombres y mujeres. Según el índice de masa corporal (IMC), 32,5 % de la población presentó sobrepeso; 35 % obesidad grado I; 22 % grado II y 9 % grado III. Al evaluar el perímetro de cintura (PC), el 98,7 % superó los puntos de corte. El índice cintura/ talla superó el valor normal en ambos sexos, siendo significativamente superior en las mujeres (p: 0,003). Conclusiones: En la población de adultos mayores que se estudió no se observó diferencia entre ambos sexos en el número de componentes diagnósticos de SM. En cuanto al perímetro de cintura, el valor fue similar en ambos sexos, lo que podría llevar a revisar el valor de corte del mismo en este grupo etario. El ICT estuvo aumentado en toda la población y por ser un subrogante de riesgo cardiovascular, sería otro parámetro a tener en cuenta al momento del diagnóstico de SM. Rev Argent Endocrinol Metab 51:130-135, 2014 Los autores no poseen conflictos de interés.

Introduction: The metabolic syndrome (MS) denotes an association of abnormalities that increase the risk of cardiovascular disease. With the intention of decreasing this risk, international organizations have dropped the normal range for various parameters, with a consequent increase in the diagnosis of MS. Although the changes related to age are well documented, none of these parameters has been age-adapted. Aims: to characterize MS in the elderly population and to establish possible gender differences. Materials and methods: We performed a prospective study in patients who presented at the Department of Endocrinology of the Healthcare Unit Dr. Cesar Milstein. Of the total population, 68.8 % were women and the average age was 73 ± 6 years. For the diagnosis of MS, we used the 2009 Joint Interim Statement diagnostic criteria. Information was collected on previous history and medication, and laboratory analyses were performed. The waist / height ratio was also measured. Mean ± standard deviation (SD) and proportions were calculated. For comparisons between men and women, the Student test and Chi-squared test were used. Results: Of the total population, 42.9 % fulfilled 3 criteria for MS, 33.8 % fulfilled 4 criteria and 23.4 % fulfilled 5, with similar distribution in men and women. According to body mass index (BMI), 32.5 % of the population had overweight, 35 % were grade I obese, 22 % were grade II and 9 % were grade III. As regards waist circumference, 98.7 % of the total population exceeded the established cutoffs. The waist/ height ratio exceeded normal values in both genders, being significantly higher in women (p = 0.003). Conclusions: In the elderly, there are no gender differences in the number of components of MS. As for waist circumference, values were similar in both men and women. This finding could lead to redefine the cutoff value in aged woman. The waist / height ratio, a surrogate marker of cardiovascular disease, was ...

Registry of people with diabetes in three Latin American countries: a suitable approach to evaluate the quality of health care provided to people with type 2 diabetes.

AIMS: To implement a patient registry and collect data related to the care provided to people with type 2 diabetes in six specialized centers of three Latin American countries, measure the quality of such care using a standardized form (QUALIDIAB) that collects information on different quality of care indicators, and analyze the potential of collecting this information for improving quality of care and conducting clinical research. METHODS: We collected data on clinical, metabolic and therapeutic indicators, micro- and macrovascular complications, rate of use of diagnostic and therapeutic elements and hospitalization of patients with type 2 diabetes in six diabetes centers, four in Argentina and one each in Colombia and Peru. RESULTS: We analyzed 1157 records from patients with type 2 diabetes (Argentina, 668; Colombia, 220; Peru, 269); 39 records were discarded because of data entry errors or inconsistencies. The data demonstrated frequency performance deficiencies in several procedures, including foot and ocular fundus examination and various cardiovascular screening tests. In contrast, HbA1c and cardiovascular risk factor assessments were performed with a greater frequency than recommended by international guidelines. Management of insulin therapy was sub-optimal, and deficiencies were also noted among diabetes education indicators. CONCLUSIONS: Patient registry was successfully implemented in these clinics following an interactive educational program. The data obtained provide useful information as to deficiencies in care and may be used to guide quality of care improvement efforts.

The amygdala to periaqueductal gray pathway: plastic changes induced by audiogenic kindling and reversal by gabapentin.

Repeated, periodic induction of AGS (AGS kindling) in GEPR-9s increases seizure duration and induces an additional generalized clonus phase [post-tonic clonus (PTC)], which involves expansion of the localized brainstem AGS network to the amygdala. The pathway between central amygdala (CeA) and ventrolateral periaqueductal gray (vlPAG) is implicated in several disorders, including pain and anxiety. This pathway is also implicated in the network of audiogenic seizures (AGS) in genetically epilepsy-prone rats (GEPR-9s). We examined AGS kindling-induced changes in vlPAG extracellular action potentials evoked by electrical stimuli in CeA in awake, behaving GEPR-9s, using chronically-implanted stimulation electrodes in CeA and microwire recording electrodes in vlPAG. The effect of gabapentin, an anticonvulsant drug that is also effective in pain and anxiety disorders, on the CeA to vlPAG pathway in AGS-kindled GEPR-9s was also evaluated. Electrical stimulation in CeA evoked consistent, short latency and intensity-dependent vlPAG neuronal firing increases. However, in AGS-kindled GEPR-9s these responses showed a precipitous firing increase with increasing stimulus intensity, as compared to non-kindled GEPR-9s. Gabapentin (50mg/kg, i.p.) significantly reduced vlPAG neuronal responses to CeA stimulation to pre-AGS-kindled levels and reversibly blocked PTC in AGS-kindled GEPR-9s. These data suggest that the amygdala to vlPAG pathway may be critical in mediating the emergence of PTC during AGS kindling. The ability of gabapentin to suppress this pathway may be important for its anticonvulsant effects in AGS-kindled GEPR-9s, and this effect may contribute to gabapentin's effectiveness in anxiety and pain in which the amygdala to PAG pathway is also implicated.

Neurons in the periaqueductal gray are critically involved in the neuronal network for audiogenic seizures during ethanol withdrawal.

The periaqueductal gray (PAG) is implicated in the network subserving audiogenic seizures (AGS). AGS are seen during ethanol withdrawal (ETX), and the present study examined effects of focal NMDA receptor blockade in PAG during ETX and PAG neuronal firing changes associated with ETX. Bilateral cannulae or microwire electrodes were chronically implanted into PAG. Ethanol was administered intragastrically at 8-h intervals for 4 days, resulting in AGS susceptibility during ETX. Microinjection of a competitive NMDA receptor antagonist, DL-2-amino-7-phosphonoheptanoic acid (AP7) (2 and 5 but not 1 nmol/side), into the PAG suppressed AGS, in part, reversibly. In microwire experiments spontaneous and acoustically evoked PAG neuronal responses in behaving rats were reduced significantly 1 h after initial administration of ethanol. During ETX, when the animals were susceptible to AGS, significant increases in spontaneous and acoustically evoked PAG neuronal firing occurred. PAG neurons exhibited burst firing 2-4 s prior to the tonic-clonic phase of AGS and tonic repetitive firing during this seizure phase, which ceased during post-ictal depression. Increased NMDA receptor function in PAG may be important to the aberrant PAG neuronal firing in AGS, since previous studies observed upregulation of NMDA receptors during ETX, and the present study observed that focal microinjection of a NMDA antagonist into PAG blocked AGS.

Neurons in the deep layers of superior colliculus are a requisite component of the neuronal network for seizures during ethanol withdrawal.

Ethanol withdrawal (ETX) in ethanol-dependent animals and humans often results in seizure susceptibility. The deep layers of superior colliculus (DLSC) are proposed to be involved in the neuronal networks of several types of seizures. In rodents, ETX results in susceptibility to audiogenic seizures (AGS), and the DLSC are implicated as a critical component of the seizure network in a genetic form of AGS. Ethanol inhibits NMDA receptors, and the binding at these receptors is increased during ETX in certain brain regions. Therefore, the effect of focal microinjection into DLSC of a competitive NMDA receptor antagonist, DL-2-amino-7-phosphonoheptanoic acid (AP7) on ETX seizures was examined. AP7 (2 and 5 nmol/side) microinjected bilaterally into DLSC suppressed AGS, supporting a critical role of the DLSC in the AGS network during ETX. DLSC neuronal firing changes in behaving rats were subsequently examined, using chronically implanted microwire electrodes. Acoustically-evoked DLSC firing was significantly suppressed during ethanol intoxication and during ETX. However, DLSC neurons began firing tonically 1-2 s before the onset of the wild running behavior of AGS. Acoustically-evoked DLSC firing was suppressed during post-ictal depression with recovery beginning as the righting reflex returned. These data support a requisite role of the DLSC in AGS during ETX. These neuronal firing changes suggest an important role of DLSC neurons in generation of the wild running phase of AGS during ETX, which may be a general pathophysiological mechanism and a critical event in the initiation of wild running, since a similar pattern was seen previously in a genetic form of AGS.

Modulation of audiogenically kindled seizures by gamma-aminobutyric acid-related mechanisms in the amygdala.

Repetitive induction of audiogenic seizures (AGSs) ("AGS kindling") results in expansion of the AGS neuronal network from the brainstem to forebrain structures. AGSs in kindled genetically epilepsy-prone rats (GEPR-9s) exhibit a significant increase in the duration of posttonic clonus (PTC). The amygdala (AMG) does not appear to be a required network component before AGS kindling, but this structure is implicated in the seizure network after AGS kindling. gamma-Aminobutyric acid (GABA) is a major neurotransmitter in AMG, and histamine receptor activation is also reported to stimulate GABA release. The present study examined the effect on audiogenically kindled seizures of focal microinjections into the AMG of GEPR-9s. AGS kindling involved induction of 14 AGSs in GEPR-9s. Bilateral microinjection of a GABA(A) agonist, muscimol (0.3 nmol/side), into the AMG significantly reduced the duration of PTC, starting 0.5 h after drug infusion, with recovery by 24 h. Microinjection of histamine (60 nmol/side) suppressed PTC at 0.5 h, with total blockade at 24 h, but the seizure pattern did not revert to that observed before kindling until 120 h. This long duration suggests that mechanisms in addition to modulation of GABA function may be involved in the effect of histamine. The wild running and tonic components of AGS were never affected by microinjection of these agents into the AMG. These findings confirm previous work suggesting that the AMG is not a required nucleus in the AGS neuronal network before kindling. However, the AMG becomes critical in expansion of the seizure network during AGS kindling, and audiogenically kindled seizures are negatively modulated by increased GABA function.

Audiogenic seizure susceptibility is induced by termination of continuous infusion of gamma-aminobutyric acid or an N-methyl-D-aspartic acid Antagonist into the inferior colliculus.

The inferior colliculus (IC) is strongly implicated in seizure initiation in a genetic form of audiogenic seizures (AGS) and in AGS observed during ethanol withdrawal (ETX). Ethanol is known to block the actions of excitatory amino acids (EAA) and enhance the actions of gamma-aminobutyric acid (GABA) in several brain areas, including the IC. The present study investigated the effects on susceptibility to AGS following withdrawal from continuous blockade of N-methyl-D-aspartic acid (NMDA) receptors or continuous activation of GABA receptors in the IC. This involved infusion of GABA (1 M) or a competitive NMDA antagonist, DL-2-amino-7-phosphonoheptanoic acid (AP7, 1 mM), at 0.25 microl/h for 7 days using an Alzet osmotic minipump. Following abrupt termination of the infusion, AGS susceptibility began at 30 min. The incidence of AGS was 38.9 and 56.3% following GABA and AP7 withdrawal, respectively. The AGS behaviors observed during withdrawal, which included wild running and bouncing clonus, were very similar to those evoked by acoustic stimuli during ETX. AGS susceptibility lasted for several hours and in 13% of animals persisted for up to 6 months. The current results support diminished GABAergic and elevated glutamatergic function in the IC as the critical mechanisms and sites for AGS initiation. The present study, coupled with previous evidence that chronic ethanol exposure reduced GABA-mediated inhibition and enhanced EAA-mediated excitation, suggests that these amino acid receptor-mediated alterations in the IC are key elements in initiating AGS during ethanol withdrawal.

Inferior colliculus intracellular response abnormalities in vitro associated with susceptibility to ethanol withdrawal seizures.

During ethanol withdrawal (ETX), rats become susceptible to audiogenic seizures in which the inferior colliculus (IC) is known to play a critical role. The present study examined changes in membrane properties that occurred in IC dorsal cortex (ICd) neurons in brain slices from rats after 4 days of three times daily intragastric ethanol, which is proposed to be an analog of binge drinking. Compared with neurons from control animals, ICd neurons during ETX had action potentials (APs) with lower thresholds, a greater incidence of spontaneous APs, a reduced degree of spike firing adaptation, and an increased incidence of anode-break firing. With synaptic stimulation, epileptiform firing was seen in nearly 50% of ICd neurons during ETX but never was seen in normal ICd neurons except after perfusion of the gamma-aminobutyric acid type A (GABA(A)) antagonist bicuculline. Paired pulse responses of ICd neurons were also abnormal during ETX. Thus, in 75% of normal rats, paired synaptic stimuli inhibited the second response, but during ETX all neurons tested showed paired pulse facilitation. These aberrant membrane and synaptic properties provide direct evidence for the hyperexcitability of IC neurons during ETX. They may be due, in part, to changes in GABAergic and glutamatergic neurotransmission known to be produced during withdrawal after continued ethanol administration.

Decreased GABA and increased glutamate receptor-mediated activity on inferior colliculus neurons in vitro are associated with susceptibility to ethanol withdrawal seizures.

Cessation of ethanol administration in ethanol-dependent rats results in an ethanol withdrawal (ETX) syndrome, including audiogenic seizures (AGS). The inferior colliculus (IC) is the initiation site for AGS, and membrane properties of IC neurons exhibit hyperexcitability during ETX. Previous studies observed that ETX alters GABA and glutamate neurotransmission in certain brain sites. The present study evaluated synaptic properties and actions of GABA or glutamate antagonists during ETX in IC dorsal cortex (ICd) neurons in brain slices from rats treated with ethanol intragastrically 3 times daily for 4 days. A significant increase of spontaneous action potentials (APs) was observed during ETX. The width, area and rise time of excitatory postsynaptic potentials (EPSPs) evoked by stimulation in the commissure of IC were significantly elevated during ETX. A fast EPSP was sensitive to block by the non-NMDA receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), and a slow EPSP was sensitive to the NMDA receptor antagonist, 2-amino-5-phosphonovalerate (AP5). However, during ETX the concentration of CNQX or AP5 needed to block these EPSPs was elevated significantly. Inhibitory postsynaptic potentials (IPSPs) in ICd neurons evoked in both normal and ETX rats were blocked by the GABA(A) antagonist, bicuculline. However, IPSPs during ETX displayed a significantly greater sensitivity to bicuculline. These data indicate that decreased GABA(A)-mediated inhibition and increased glutamate-mediated excitability in IC may both be critical mechanisms of AGS initiation during ETX, which is similar to observations in a genetic form of AGS. The common changes in IC neurotransmission in these AGS forms may be general mechanisms subserving AGS and other forms of auditory system pathophysiology in which the IC is implicated.

Modulation of audiogenic seizures by histamine and adenosine receptors in the inferior colliculus.

Susceptibility to behaviorally similar audiogenic seizures (AGS) occurs genetically and is inducible during ethanol withdrawal (ETX). Comparisons between AGS mechanisms of genetically epilepsy-prone rats (GEPR-9s) and ethanol-withdrawn rats (ETX-Rs) are yielding information about general pathophysiological mechanisms of epileptogenesis. The inferior colliculus (IC) is the AGS initiation site. Excitatory amino acid (EAA) abnormalities in the IC are implicated in AGS, and histamine and adenosine receptor activation each reduce EAA release and inhibit several seizure types. Previous studies indicate that focal infusion of an adenosine receptor agonist into the IC blocked AGS in GEPR-9s, but the effects of adenosine receptor activation in the IC on AGS in ETX-Rs are unknown. The effects of histamine receptor activation on either form of AGS are also unexamined. The present study evaluated effects of histamine or a nonselective adenosine A(1) agonist, 2-chloroadenosine, on AGS by focal microinjection into the IC. Ethanol dependence and AGS susceptibility were induced in normal rats by intragastric ethanol. Histamine (40 or 60 nmol/side) significantly reduced AGS in GEPR-9s, but histamine in doses up to 120 nmol/side did not affect AGS in ETX-Rs. 2-Chloroadenosine (5 or 10 nmol/side) did not affect AGS in ETX-Rs, despite the effectiveness of lower doses of this agent in GEPR-9s reported previously. Thus, histamine and adenosine receptors in the IC modulate AGS of GEPR-9s, but do not modulate ETX-induced AGS. The reasons for this difference may involve the chronicity of AGS susceptibility in GEPR-9s, which may lead to more extensive neuromodulation as compensatory mechanisms to limit the seizures compared to the acute AGS of ETX-Rs.

Phenytoin administration reveals a differential role of pontine reticular formation and periaqueductal gray neurons in generation of the convulsive behaviors of audiogenic seizures.

The ventrolateral periaqueductal gray (PAG) and pontine reticular formation (PRF) are implicated in the neuronal network for audiogenic seizures (AGS). The AGS of genetically epilepsy-prone rats (GEPR-9s) culminate in tonic hindlimb extension (TE), and elevated acoustically evoked neuronal firing and burst firing, immediately preceding TE, have been observed in PAG and PRF. This study examined changes in PAG and PRF neuronal firing and behavior in GEPR-9s, following phenytoin administration. Recordings involved 16 PAG and nine PRF neurons in GEPR-9s. Phenytoin in doses (mean, 6. 3 mg/kg) that suppressed TE selectively did not consistently alter PAG neuronal firing. However, these doses of phenytoin resulted in significant (51.6% of control) suppression of PRF neuronal firing. Doses of phenytoin (mean, 8.3 mg/kg), which completely blocked AGS, significantly reduced PAG neuronal firing (64.6% of control), and more greatly suppressed PRF firing (25.8% of control). These results are consistent with a critical role for PRF neurons in generation of TE not evident for PAG. The suppression of PAG and PRF neuronal firing induced by phenytoin with complete seizure blockade is consistent with vital roles for both structures in the seizure network. The differential effects of phenytoin on structures requisite to the seizure network indicate that this experimental approach may be able to identify the most sensitive therapeutic target for anticonvulsant drugs, which could be critical to pharmacological suppression of specific seizure behaviors manifest in various types of convulsions, potentially including human epilepsy.

Synaptic response patterns of neurons in the cortex of rat inferior colliculus.

The present study examined synaptic potentials of neurons in inferior colliculus (IC) cortex slice and the roles of GABA and glutamate receptors in generating these potentials. Multipolar (82%) and elongated (18%) cells were observed with intracellular biocytin staining. Electrical stimulation of the IC commissure (CoIC) elicited only inhibitory postsynaptic potentials (IPSPs) (10% of cells), only excitatory postsynaptic potentials (EPSPs) (51%), or both (38%). IPSPs were elicited at lower thresholds and shorter latencies than EPSPs (mean: 1.6+/-1.2 ms) and IPSPs were observed in all neurons following membrane depolarization. Short-latency EPSPs were blocked by non-NMDA receptor antagonists, and longer-latency EPSPs were blocked by NMDA antagonists. CoIC stimulation evoked short-latency IPSPs (mean: 0.55+/-0.33 ms) in 48% of neurons, and the IPSPs persisted despite glutamate receptor blockade, which implies monosynaptic inhibitory input. A GABA(A) antagonist blocked IPSPs and paired pulse inhibition of EPSPs, suggesting GABA(A) receptor mediation. A GABA(B) antagonist reduced paired pulse inhibition of IPSPs, suggesting GABA(B) receptor modulation. Thus, GABA-mediated inhibition plays a critical role in shaping synaptic responses of IC cortex neurons. Normal GABAergic function in IC has been shown to be important in acoustic coding, and reduced efficacy of GABA function in IC neurons is critical in IC pathophysiology in presbycusis, tinnitus and audiogenic seizures.

Neuronal networks in the genetically epilepsy-prone rat.

It is now possible to develop a dynamic neuronal network model for generalized convulsive seizures because of in vivo data recently obtained in a naturally occurring epilepsy model--the genetically epilepsy-prone rats (GEPR-9s). GEPR-9s exhibit audiogenic seizures (AGS) that consist of a sequence of discrete behavioral phases (i.e., wild running, clonus-tonus, and post-ictal depression). The neuronal firing changes in most nuclei implicated in the network during each phase of AGS in behaving GEPR-9s have been examined. The inferior colliculus is critical in AGS initiation, because extensive firing increases in inferior colliculus are observed preceding seizure initiation. The deep layers of superior colliculus (DLSC) are crucial to wild running, based on the emergence of tonic firing of DLSC neurons just preceding this phase. The pontine reticular nucleus (PRF) and periaqueductal gray (PAG) are critical to the clonic-tonic phase, because tonic firing patterns appear in these neurons just prior to this phase. During post-ictal depression all areas except the PRF are quiescent. These temporal relationships suggest that each nucleus plays a specific hierarchic role in each discrete convulsive behavior. Generalized tonic-clonic seizure behavior observed in human epilepsy, in GEPR-9s, and in other seizure models is likely to involve similar neuronal network components. The neurotransmitter mechanisms subserving the abnormal neuronal responses in the GEPR-9 neuronal network involve an increased availability of glutamate and a decrease in the effectiveness of gamma-aminobutyric acid (GABA) in many brain regions. Focal modification of the effects of GABA, glutamate, norepinephrine, or serotonin also modulates the nuclei of the network differentially. Together, these data reveal the anatomic, neurotransmitter, and neurophysiologic mechanisms of the neuronal network hierarchy in GEPR-9s, which is currently the most completely developed of any generalized convulsive model. Differential effects of anticonvulsants on the AGS phases and concomitant differential modifications of neuronal firing are observed on neurons in these network nuclei. With nearly complete identification of the network nuclei, the differential effects of these anticonvulsant drugs on different aspects of neuronal firing in different brain sites indicate that this experimental approach can likely identify the most sensitive therapeutic target for these agents. This concept is potentially vital to developing the most selective treatment of different convulsive behaviors occurring in human epilepsy. The neuronal network for AGS does not require brain structures rostral to the midbrain for seizure expression. However, the forebrain is recruited into an expanded seizure network through AGS repetition ("kindling"), resulting in prolonged AGS, post-tonic clonus, and epileptiform electrographic cortical abnormalities. AGS kindling produces network expansion into medial geniculate body (MGB) and amygdala and involves neuronal firing increases in MGB.

The periaqueductal grey is a critical site in the neuronal network for audiogenic seizures: modulation by GABA(A), NMDA and opioid receptors.

The nuclei comprising the neuronal network for audiogenic seizures (AGS) are located primarily in the brainstem. Previous studies suggested a role for the periaqueductal grey (PAG) in the AGS network. The present study evaluated this possibility in genetically-epilepsy prone rats (GEPR-9s) by examining the effects of bilateral focal microinjection of a competitive NMDA receptor antagonist (DL-2-amino-7-phosphonoheptanoic acid (AP7), 1 and 5 nmol/side), a GABA(A) agonist (gaboxedol (THIP), 10 and 15 nmol) or an opioid peptide receptor antagonist (naloxone, 5 nmol) into PAG, based on the proposed role of these receptors in PAG neurotransmission. Blockade of NMDA receptors by AP7 (both doses) or activation of GABA(A) receptors with THIP (15 nmol/side) in the PAG suppressed AGS susceptibility. Naloxone displayed a seizure-suppressant effect that was delayed and incomplete. The seizure suppressant effect of AP7 or naloxone, unlike THIP, was observed at doses that did not produce motor quiescence. These data suggest that the PAG is a requisite nucleus in the neuronal network for AGS in GEPR-9s and that GABA(A), opioid peptide and NMDA receptors in the PAG modulate AGS propagation.

Differential roles in the neuronal network for audiogenic seizures are observed among the inferior colliculus subnuclei and the amygdala.

The inferior colliculus (IC) is established as the initiation site within the neuronal network for audiogenic seizures (AGS), but the relative importance of the IC subnuclei in AGS is controversial. The lateral and basolateral subdivisions of the amygdala are implicated in the expansion of the AGS network that occurs during AGS kindling. However, the role of the amygdala in the AGS network in nonkindled AGS is unknown. NMDA receptors are implicated in modulation of AGS and in neurotransmission in both the IC and amygdala. Therefore, changes in AGS severity in genetically epilepsy-prone rats (GEPR-9s) were examined after bilateral focal microinjection into IC subnuclei or lateral/basolateral subdivisions of the amygdala of a competitive NMDA receptor antagonist, 3-((+)-2-carboxypiperazine-4-yl)propyl-1-phosphonic acid (CPP). Blockade of AGS in IC central nucleus (ICc) and external cortex (ICx) was observed at identical doses of CPP, but these doses were ineffective in IC dorsal cortex (ICd). Microinjection of CPP into the amygdala did not produce significant changes in AGS severity except at doses 20 times those effective in IC. The latter data contrast with the anticonvulsant effects of amygdala microinjections on seizure severity in kindled AGS reported previously. The present data in concord with neuronal recording studies of these nuclei suggest that the ICc is the most critical site in AGS initiation, the ICx in propagation, and that the ICd plays a lesser role in the AGS network. The amygdala does not appear to play a requisite role in the neuronal network for AGS in animals that have not been subjected to AGS kindling.

Modulation of the audiogenic seizure network by noradrenergic and glutamatergic receptors of the deep layers of superior colliculus.

Recent studies suggest that the deep layers of superior colliculus (DLSC) play a role in the network for audiogenic seizures (AGS) in genetically epilepsy-prone rats (GEPR-9s). The present study examined the role of glutamatergic and noradrenergic receptors in DLSC in modulation of AGS susceptibility. The study examined effects of a competitive NMDA receptor antagonist [dl-2-amino-7-phosphonoheptanoic acid (AP7)] or an alpha1 noradrenergic agonist (phenylephrine) focally microinjected into DLSC as compared to effects in the inferior colliculus (IC) and pontine reticular formation (PRF), which are major established components of the AGS network. The results demonstrated that blockade of NMDA receptors in DLSC suppressed AGS susceptibility. AP7 microinjection was effective at relatively low doses in IC, but required higher doses in DLSC and PRF. The DLSC was relatively more sensitive to seizure reduction by the alpha1 noradrenergic agonist as compared to the IC and PRF. The anticonvulsant effect of AP7 was longer-lasting than phenylephrine in the DLSC and IC but not in the PRF. These data suggest that neurons in the DLSC are a requisite component for the neuronal network for AGS in GEPR-9s and that NMDA and alpha1 adrenoreceptors in this site may play important roles in the modulation of AGS propagation. The relatively greater sensitivity of DLSC to phenylephrine as compared to IC and PRF indicates that norepinephrine may be more important in the modulation of AGS in DLSC, which contrasts to the role of glutamate modulation. These data support recent neuronal recording data, which indicate that DLSC neurons play a critical role in AGS.