[Reference levels of thyroid hormones in pregnant woman from Guadalajara]. / Valores de referencia de hormonas tiroideas en la población de gestantes de Guadalajara.

INTRODUCTION: Thyroid dysfunction during gestation impacts on maternal-fetal health and may influence the neurocognitive development of the child. Thyroid physiology changes during pregnancy and requires the establishment of specific reference levels per trimester and for each population and method. The objectives of our study were to analyse thyroid function throughout pregnancy and to establish reference levels for TSH and T4L in each trimester for our population and methodology. MATERIAL AND METHODS: Prospective analytical study of 598 pregnant women from March 2018 to October 2020. TSH, T4L, T3L, ATPO and ATG were determined in all of them. A total of 151 pregnant women were excluded due to positive thyroid immunity, previous thyroid disease in treatment with levothyroxine, twin pregnancy, diagnosis of hypothyroidism and hyperthyroidism in the request or absence of some of the parameters studied, with a reference population of 447 pregnant women. RESULTS: The reference levels for TSH were 0.07-3.14mIU/L for the first, 0.66-3.21mIU/L for the second and 0.52-2.97mIU/L for the third trimester. Reference levels for T4L were 0.81-1.19ng/dL for the first, 0.71-1.07ng/dL for the second and 0.69-1.06ng/dL for the third trimester. CONCLUSIONS: The reference levels for TSH and T4L obtained in this study differ from those used for the general population, which may have led to misclassification errors and unnecessary treatment in pregnant women.

Effect of a high-fat diet and leptin on STAT3 phosphorylation in hippocampal astrocytes.

OBJECTIVE: The aim of the current study was to evaluate the influence of HFD on the functionality of LepR by quantifying phosphorylated levels of 705Tyr-STAT3 in hippocampus astrocytes from mice that consumed an HFD either during the juvenile or the adult period. METHODS: Five- and eight-week-old male mice, fed during 8 weeks with either control chow or HFD, received a single dose of leptin and their brains were prepared for immunofluorescence to identify double-positive GFAP/p705Tyr-STAT3 cells. RESULTS: HFD intake led to increased pSTAT3 immunoreactivity in GFAP+ cells in the CA1/CA3 hippocampus areas. The effect was observed both in adolescent and adult mice. Leptin increased pSTAT3 immunoreactivity in control animals but was devoid of effect in HFD mice. HFD itself has no effect on the number of GFAP+ cells. CONCLUSIONS: Our data show that regular intake of HFD enhances STAT3 signaling in CA1/CA3 astrocytes, an effect that could be linked to the increase of leptin triggered by HFD. The increase of pSTAT3 might be integral to homeostatic mechanisms aimed at maintaining hippocampus function.

Saturated and unsaturated fat diets impair hippocampal glutamatergic transmission in adolescent mice.

Consumption of high-fat diets (HFD) has been associated with neuronal plasticity deficits and cognitive disorders linked to the alteration of glutamatergic disorders in the hippocampus. As young individuals are especially vulnerable to the effects of nutrients and xenobiotics on cognition, we studied the effect of chronic consumption of saturated (SOLF) and unsaturated oil-enriched foods (UOLF) on: i) spatial memory; ii) hippocampal synaptic transmission and plasticity; and iii) gene expression of glutamatergic receptors and hormone receptors in the hippocampus of adolescent and adult mice. Our results show that both SOLF and UOLF impair spatial short-term memory. Accordingly, hippocampal synaptic plasticity mechanisms underlying memory, and gene expression of NMDA receptor subunits are modulated by both diets. On the other hand, PPARγ gene expression is specifically down-regulated in adolescent SOLF individuals and up-regulated in adult UOLF mice.

Effects of chronic cocaine treatment during adolescence in Lewis and Fischer-344 rats: Novel location recognition impairment and changes in synaptic plasticity in adulthood.

The use of Lewis (LEW) together with Fischer-344 (F344) rats has been proposed as an addiction model because of the addiction behavior differences of these two strains. We have previously suggested that these differences could be related to learning and memory processes and that they depend on the genetic background of these two strains of rats. Adolescence is a period of active synaptic remodeling, plasticity and particular vulnerability to the effects of environmental insults such as drugs of abuse. We have evaluated spatial memory using novel location recognition in LEW and F344 adult rats undergoing a chronic treatment with cocaine during adolescence or adulthood. In order to study whether synaptic plasticity mechanisms were involved in the possible changes in learning after chronic cocaine treatment, we carried out electrophysiological experiments in hippocampal slices from treated animals. Our results showed that, in LEW cocaine-treated rats, hippocampal memory was only significantly impaired when the drug was administered during adolescence whereas adult administration did not produce any detrimental effect in spatial memory measured in this protocol. Moreover, F344 rats showed clear difficulties carrying out the protocol even in standard conditions, confirming the spatial memory problems observed in previous reports and demonstrating the genetic differences in spatial learning and memory. Our experiments show that the effects in behavioral experiments are related to synaptic plasticity mechanisms. Long-term depression induced by the glutamate agonist NMDA (LTD-NMDA) is partially abolished in cocaine-treated animals in hippocampal slices from LEW rats. Hippocampal LTD-NMDA is partially inhibited in F344 animals regardless of whether saline or cocaine administration, suggesting the lack of plasticity of this strain that could be related to the inability of these animals to carry out the novel object location protocol.

Cocaine facilitates protein synthesis-dependent LTP: the role of metabotropic glutamate receptors.

Cocaine addiction alters synaptic plasticity in many brain areas involved in learning and memory processes, including the hippocampus. Long-term potentiation (LTP) is one of the best studied examples of hippocampal synaptic plasticity and it is considered as one of the molecular basis of learning and memory. We previously demonstrated that in the presence of cocaine, a long lasting form of hippocampal LTP is induced by a single pulse of high frequency stimulation, which in normal conditions evokes only an early form of LTP. In this study, we further explore the molecular basis of this modulation of synaptic plasticity by cocaine. By performing pharmacological experiments on hippocampal slices, we were able to show that cocaine converts early LTP to a form of LTP dependent on protein synthesis, probably through the cAMP-dependent protein kinase and extracellular signal-regulated kinase signaling cascades. We also found that metabotropic glutamate receptors are involved in this phenomenon. These studies further clarify the molecular machinery used by cocaine to alter synaptic plasticity and modulate learning and memory processes.

Depotentiation of hippocampal long-term potentiation depends on genetic background and is modulated by cocaine self-administration.

Lewis (LEW) and Fischer 344 (F344) rats differ in their response to drugs and are frequently used as an experimental model to study vulnerability to drug addiction. We have previously reported that significant differences in hippocampal synaptic plasticity exist between LEW and F344 rats after non-contingent chronic cocaine administration. However, given the several biochemical differences between contingent and non-contingent administration of drugs, we have studied here the possible genetic differences in synaptic plasticity after contingent cocaine self-administration. LEW and F344 animals self-administered cocaine (1 mg/kg i.v.) or saline under a fixed ratio 1 schedule of reinforcement for 20 days. After self-administration, electrophysiological experiments were carried out in which hippocampal slices were tetanized with three high frequency pulses in order to induce long-term potentiation (LTP). After a 20 min period of LTP stabilization, a train of low frequency stimulation (LFS; 900 pulses, 1 Hz) was applied to induce depotentiation of LTP. Data showed no differences between cocaine self-administered LEW or F344 rats in the induction of saturated-LTP compared to saline animals. LEW saline self-administered rats showed normal LTP depotentiation whereas cocaine self-administration impaired depotentiation in this rat strain. In the F344 strain, depotentiation of saturated-LTP was impaired both in saline and cocaine self-administered rats. The present results corroborate previous findings showing differences in basal hippocampal synaptic plasticity between LEW and F344 rats. These differences seem to modulate cocaine effects in a manner independent of contingency of drug administration.

High-fat diets impair spatial learning in the radial-arm maze in mice.

It has been suggested that hyperglycemia and insulin resistance triggered by energy-dense diets can account for hippocampal damage and deficits of cognitive behaviour. We wonder if the impairment of learning and memory processes detected in diet-induced obese (DIO) mice is linked to diet composition itself. With this purpose we have evaluated learning performance in mice undergoing a short-term high-fat (HF) treatment, which leads to a pre-obese state characterized by increased adiposity without significant changes of glucose and insulin plasma levels. C57BL/6J mice were fed either a HF (45 kcal% from fat) or control diet (10 kcal% from fat) during 8 weeks. Learning performance was evaluated by using the four-arm baited version of the eight-arm radial maze test (RAM). Mice were trained to learn the RAM protocol and then memory was tested at different time-points. Time spent to consume food placed in baited arms and errors committed to find them were measured in all sessions. DIO mice significantly spent more time in learning the task and made a greater number of errors than controls. Moreover, retention tests revealed that both working and total memory errors were also more numerous in DIO mice. The current results show that short-term DIO impairs spatial learning and suggest that impairment of hippocampal learning elicited by HF diets might be perceptible before metabolic alterations linked to obesity develop.

Chronic periadolescent cannabinoid treatment enhances adult hippocampal PSA-NCAM expression in male Wistar rats but only has marginal effects on anxiety, learning and memory.

Pubertal and adolescent exposure to cannabinoids is associated with enduring alterations in anxiety and memory. However, periadolescence virtually remains unexplored. Here, we measured anxiety in the Elevated Plus Maze (EPM) in adult Wistar rats treated at periadolescence (P28-P38) with the cannabinoid agonist CP 55,940 (CP) (0.4 mg/kg; 2 ml/kg i.p., 1 daily injection), and we also defined their recognition memory in the novel object paradigm and spatial learning and memory in the water maze. Additionally, we measured the expression of hippocampal PSA-NCAM (Polysialic Acid-Neural Cell Adhesion Molecule) and long-term potentiation (LTP) as well as, given their role in mnemonic processing, the levels of plasma corticosterone and estradiol. We found that CP had no robust effects on anxiety or in recognition memory. In the water maze, only a slight decreased percentage of failed trials in the reference memory task and an improvement in an indirect index of attention were observed. However, we detected an up-regulation of hippocampal PSA-NCAM expression, only in CP-males, although this effect was not related to changes in LTP. No hormonal alterations were evident. Based on our data, minimal long-term effects on anxiety, learning and memory appear to result from cannabinoid exposure during the periadolescent period.

Genetic differences in hippocampal synaptic plasticity.

Synaptic plasticity is considered a physiological substrate for learning and memory [Lynch MA (2004) Long-term potentiation and memory. Physiol Rev 84:87-136] that contributes to maladaptive learning in drug addiction [Schoenbaum G, Roesch MR, Stalnaker TA (2006) Orbitofrontal cortex, decision-making and drug addiction. Trends Neurosci 29:116-124]. Many studies have revealed that drug addiction has a strong hereditary component [Kosten TA, Ambrosio E (2002) HPA axis function and drug addictive behaviors: insights from studies with Lewis and Fischer 344 inbred rats. Psychoneuroendocrinology 27:35-69; Uhl GR (2004) Molecular genetic underpinnings of human substance abuse vulnerability: likely contributions to understanding addiction as a mnemonic process. Neuropharmacology 47 (Suppl 1):140-147], however the contribution of the genetic background to drug-induced changes in synaptic plasticity has been scarcely studied. The present study reports on an analysis of long-term potentiation (LTP) and depotentiation in Lewis (LEW) and Fischer-344 (F344) rats, two inbred rat strains that show different proneness to drugs of abuse and are considered an experimental model of genetic vulnerability to addiction [Kosten TA, Ambrosio E (2002) HPA axis function and drug addictive behaviors: insights from studies with Lewis and Fischer 344 inbred rats. Psychoneuroendocrinology 27:35-69]. The induction of saturated-LTP was similar in LEW and F344 rats treated with saline or cocaine. However, only slices from LEW saline-treated rats showed the reversal of LTP; thus, the depotentiation of saturated-LTP was not observed in cocaine-injected LEW rats and in F344 animals (treated either with cocaine or saline). These results suggest significant differences in hippocampal synaptic plasticity between Lewis and Fischer 344 rats.

Glutamate and aspartate levels in the nucleus accumbens during cocaine self-administration and extinction: a time course microdialysis study.

RATIONALE: Accumbal excitatory amino acid (EAA) transmission has been implicated in cocaine addiction. However, the time course effects of extinction of cocaine self-administration on EAAs are unknown. OBJECTIVES: The objective of this study was to define the time course of cocaine self-administration and extinction effects on glutamate and aspartate levels in the nucleus accumbens. MATERIALS AND METHODS: Rats were trained to self-administer cocaine for 20 days, and the levels of extracellular glutamate and aspartate were measured by in vivo microdialysis both during cocaine self-administration and after a priming cocaine injection at different time points after extinction (1, 5, or 10 days). A food-reinforced control group was also included in this study. Furthermore, the effect of acute i.v. cocaine administration (0, 1, 2, or 4 mg/kg) on glutamate and aspartate levels was also evaluated. RESULTS: At any of the dose tested, acute i.v. cocaine did not affect the levels of glutamate or aspartate in the Nacc. In contrast, glutamate levels were reduced in animals trained to self-administer cocaine, although they augmented substantially during a subsequent session of cocaine self-administration, and similar changes were not observed in food-reinforced controls. After 1 or 5, but not after 10 days of extinction, the glutamate levels were also reduced, and the ability of i.v. cocaine priming injections to increase glutamate levels followed a similar time course. These effects were specific, as aspartate levels were not affected by any administration protocol. CONCLUSIONS: These data suggest that glutamatergic transmission could be involved in the maintenance of cocaine self-administration and in the early phases of abstinence.

Cocaine self-administration improves performance in a highly demanding water maze task.

RATIONALE: Long-term potentiation (LTP) is considered to be a cellular substrate of learning and memory. Indeed, the involvement of LTP-like mechanisms in spatial learning has consistently been demonstrated in the Morris water maze test. We have previously shown that hippocampal LTP in Lewis rats was modulated by cocaine self-administration, although the performance of cocaine-self-administered rats in the Morris water maze was not altered. OBJECTIVE: Given that the ease of the task previously used could have masked any possible effects of the cocaine-induced LTP enhancement on spatial learning, a new and more difficult water maze task was devised to address this issue. MATERIALS AND METHODS: Animals self-administered cocaine (1 mg/kg) or saline under a fixed ratio 1 schedule of reinforcement for 22 days. Spatial learning was assessed in a difficult water maze task (four sessions, two trials per session with a 90-min intertrial interval), and spatial memory was also evaluated 48 h after training (a 90-s test). Additionally, reversal learning and perseverance were also studied. RESULTS: There was a reduced latency in finding the hidden platform during training, as well as improved memory of the platform location in cocaine-self-administered rats with respect to animals that self-administered saline. No differences were observed in reversal learning or perseverance between groups. CONCLUSIONS: Our data suggest that cocaine self-administration facilitates learning and memory in the water maze test only when animals are submitted to highly demanding tasks, involving working memory or consolidation-like processes during the intertrial interval.

Hippocampal synaptic plasticity and water maze learning in cocaine self-administered rats.

Previously, we have shown that long-term potentiation (LTP) in hippocampus of Lewis rats was significantly modulated by cocaine self-administration. Using a single train of high-frequency stimulation of 100 Hz for 1s (HFS), we found an enhancement of LTP after cocaine self-administration that was maintained even during the extinction of this behavior. However, the effects of cocaine self-administration on a hippocampal-dependent spatial learning task were unknown. Therefore, in the present study our first objective was to analyze if cocaine self-administration might affect the performance in a hippocampus-dependent task, such as the Morris water maze test. Male adult Lewis (LEW) rats self-administered cocaine (1 mg/kg/injection) or saline (0.9% NaCl) for 3 weeks. Three hours after finishing the last self-administration session, animals were submitted to Morris water maze training for 3 consecutives days. A memory test was carried out 24 h after the last training session. No significant differences were found in escape latencies and time spent in the quadrant where the platform was located during training. Given that we did not find any cocaine effect on this spatial learning task, our second objective was to estimate indirectly if brain cocaine levels have failed to modulate LTP in animals that were performing the water maze trials. To this end, we tested if cocaine application to hippocampal slices of naïve subjects was able to evoke LTP. The results indicated that cocaine produced an enhanced LTP in these hippocampal slices. Taking together, the results of the present study suggest that hippocampal LTP-like processes generated after cocaine self-administration are not related to spatial learning hippocampal-dependent tasks, such as the water maze test.

[Neonatal management in the emergency department of a tertiary children's hospital]. / Asistencia a neonatos en el servicio de urgencias de un hospital pediátrico terciario.

OBJECTIVE: To determinate the chief complaints in neonates presenting to a pediatric emergency service and their management. MATERIAL AND METHODS: We performed a retrospective study of patients younger than 28 days old who presented to the pediatric emergency department in 2003. Patients directly admitted to the neonatal unit and those attended by the surgery and orthopedic surgery departments were excluded. Information on sex, age, time and date, waiting time, visit duration, source of referral, presenting complaint, complementary examinations, final diagnosis, and hospital admission were analyzed. RESULTS: There were 1,481 neonatal visits. The mean chronological age was 15.8 days and 57.3 % were boys. Visits were most frequent on Fridays, evening shifts, and in July and December. The most frequent chief complaints were crying/irritability (16.3 %), fever (13.6 %), vomiting (11 %), and influenza (10.8 %). The most frequent final diagnoses were feeding problems (12.6 %), infantile colic (12.4 %), and upper respiratory tract infections (12 %). No abnormalities were detected in 11.7 % of the patients and complementary examinations were not required in 45.9 %. The admission rate was 26 %, most commonly due to fever and bronchiolitis. CONCLUSIONS: Many visits were due to minor problems that did not require complementary examinations and could have been resolved in primary care. Because of the greater vulnerability of this age group, thorough investigation is required to rule out severe disease. This phenomenon was reflected by the large number of complementary examinations and admissions.

Asistencia a neonatos en el servicio de urgencias de un hospital pediátrico terciario / Neonatal management in the emergency department of a tertiary children’s hospital

Objetivo Conocer qué problemas motivan las consultas de neonatos a un servicio de urgencias y determinar las características de la atención que se les ofrece. Material y métodos Revisión retrospectiva de los informes de urgencias de los neonatos atendidos durante el año 2003. Se excluyen los pacientes que ingresaron directamente en el Servicio de Neonatología y los atendidos por las secciones de Cirugía y Traumatología. Se analizan edad, sexo, hora y fecha de llegada, tiempo de espera y asistencia, derivación por otro médico/centro, motivo de consulta, exploraciones complementarias, diagnóstico final y destino del paciente. Resultados Se realizaron 1.481 visitas, con edad media de 15,8 días. El 53,7 % eran varones. La mayor presión asistencial se registró en viernes, en el turno de tarde y en los meses de julio y diciembre. El principal motivo de consulta fue llanto/irritabilidad (16,3 %), seguido de fiebre (13,6 %), vómitos (11 %) y cuadro catarral (10,8 %). Los diagnósticos más frecuentes fueron: dudas de puericultura (12,6 %), cólico del lactante (12,4 %) e infección de vías respiratorias altas (12 %). En el 11,7 % de los casos no se objetivó ninguna patología y el 45,9 % no precisó exploraciones complementarias. La proporción de ingresos fue del 26 %, principalmente por fiebre sin foco y bronquiolitis. Conclusiones Muchas consultas corresponden a patología menor que no precisan exploraciones complementarias y podrían ser resueltas en centros de atención primaria. La alta vulnerabilidad de la etapa neonatal requiere de una valoración minuciosa por la posibilidad de procesos graves, dato reflejado en la elevada proporción de pruebas diagnósticas e ingresos

Objective To determinate the chief complaints in neonates presenting to a pediatric emergency service and their management. Material and methods We performed a retrospective study of patients younger than 28 days old who presented to the pediatric emergency department in 2003. Patients directly admitted to the neonatal unit and those attended by the surgery and orthopedic surgery departments were excluded. Information on sex, age, time and date, waiting time, visit duration, source of referral, presenting complaint, complementary examinations, final diagnosis, and hospital admission were analyzed. Results There were 1,481 neonatal visits. The mean chronological age was 15.8 days and 57.3 % were boys. Visits were most frequent on Fridays, evening shifts, and in July and December. The most frequent chief complaints were crying/irritability (16.3 %), fever (13.6 %), vomiting (11 %), and influenza (10.8 %). The most frequent final diagnoses were feeding problems (12.6 %), infantile colic (12.4 %), and upper respiratory tract infections (12 %). No abnormalities were detected in 11.7 % of the patients and complementary examinations were not required in 45.9 %. The admission rate was 26 %, most commonly due to fever and bronchiolitis. Conclusions Many visits were due to minor problems that did not require complementary examinations and could have been resolved in primary care. Because of the greater vulnerability of this age group, thorough investigation is required to rule out severe disease. This phenomenon was reflected by the large number of complementary examinations and admissions

Absceso piógeno hepático en un paciente sano / Pyogenic liver abscess in a healthy boy

No disponible

Influencia de la prueba de detección rápida del virus de la gripe en el manejo del niño febril en urgencias pediátricas / Influence of the rapid influenza virus detection test on the management of the febrile child in the paediatric emergency setting

Objetivos: Determinar las características clínicas de los pacientes diagnosticados de gripe con una prueba de detección rápida y constatar las diferencias de actuación en Urgencias con respecto a los pacientes con resultado negativo. Métodos: Revisión de las historias clínicas de aquellos pacientes a los que se solicitó una prueba de detección rápida para virus Influenza en aspirado nasofaríngeo. Resultados: Se solicitó el test en 142 pacientes (mediana de edad: 2,4 meses). Se obtuvo un resultado positivo en 63 (44,4%). La indicación principal fue fiebre asociada a clínica respiratoria (62,7%), seguida de fiebre sin foco (33,8%). De todos los pacientes con gripe sólo uno presentó un urocultivo positivo; los hemocultivos realizados y los cultivos de LCR fueron negativos. Al comparar los pacientes diagnosticados de gripe con aquéllos sin gripe no se detectaron diferencias en cuanto al sexo, edad, presencia de fiebre alta o de síntomas respiratorios. Por el contrario, los pacientes con gripe tenían menos dificultad respiratoria (1,6% vs 17,7%) y existía con más frecuencia ambiente epidémico en el domicilio (54% vs 31,6%) (p<0,01). A los pacientes con test de diagnóstico rápido positivo se les practicaron menos radiografías de tórax (30,2% vs 51,9%) (p<0,01), ingresaron menos (19% vs 57%) (p<0,001) y recibieron menos antibiótico (14,3% vs 40,5%) (p<0,001). En el subgrupo de 25 pacientes menores de 1 mes no se encontraron diferencias en ninguno de los parámetros estudiados. Conclusiones: Los pacientes con test positivo para Influenza presentan escasas características clínicas diferenciales. Disponer de técnicas de diagnóstico rápido para la gripe en Urgencias cambia el manejo diagnóstico- terapéutico en los niños de 1 a 36 meses con fiebre (AU)

Objectives: To determine the clinical characteristics of patients diagnosed with influenza with a rapid test and to study the different management in the Emergency Room with respect to the patients with a negative Influenza test. Methods: Retrospective revision of charts of those patients to whom a test of rapid detection for Influenza was ordered. Results: The test was ordered in 142 patients (median of age of 2.4 months). A positive result for the virus was obtained in 63 patients (44.4%). The main indication for the test was fever with respiratory symptoms (62.7%), followed of fever without source (33.8%). Only one patient with influenza had a positive urine culture; all the blood cultures and CSF cultures were negative. When comparing the patients with a positive test with those with a negative test we do not detect differences in sex, age, high fever or respiratory symptoms. On the other way, the patients with influenza had less respiratory distress (1.6% vs. 17.7%) and more epidemic context at home (54% vs. 31.6%) (<0.01). Patients with a positive test had a lower incidence of admission (19% vs. 57%), received less chest x-rays (30.2% vs. 51.9%) and less antibiotics (14.3% vs. 40.5%). In the sub-group of 25 patients younger than 1 month we did not find any differences. Conclusions: Patients with a positive Influenza test present small clinical differences with respect to those with a negative test. Rapid Influenza test in the Emergency setting modifies the classic management of febrile children aged 1 to 36 months (AU)

Taurine-induced synaptic potentiation and the late phase of long-term potentiation are related mechanistically.

The application of taurine (2-aminoethanesulfonic acid) induces a long-lasting increase of synaptic efficacy and axon excitability (LLP-TAU) in rat hippocampal CA1 area. After taurine withdrawal, LLP-TAU lasted at least 3 h. This fact prompted us to assess whether the mechanisms involved in the maintenance of this particular potentiation were similar to those implicated in the late phase of long-term potentiation (L-LTP). In the presence of KN-62, an inhibitor of calcium/calmodulin-dependent protein kinase, taurine perfusion (10 mM, 30 min) did not affect the induction of LLP-TAU. However, LLP-TAU maintenance was completely suppressed by KT5720, an inhibitor of the cAMP-dependent protein kinase (PKA). Moreover, the late phase of LLP-TAU was blocked by inhibiting protein synthesis with anisomycin. In addition, taurine perfusion increased the phosphorylation of cAMP response element-binding protein (CREB), although did not affect cAMP levels. These features of LLP-TAU do not appear to be caused by the activation of D1/D5 dopamine receptors, as taurine also induced synaptic potentiation in the presence of SCH23390, an antagonist of this type of receptors. Finally, the late phase of both L-LTP and LLP-TAU occluded mutually. These results suggest that taurine triggers the sequence of some of the molecular events involved in the induction of L-LTP.

Taurine activates GABA(A) but not GABA(B) receptors in rat hippocampal CA1 area.

We investigated if taurine, an endogenous GABA analog, could mimic both hyperpolarizing and depolarizing GABA(A)-mediated responses as well as pre- and postsynaptic GABA(B)-mediated actions in the CA1 region of rat hippocampal slices. Taurine (10 mM) perfusion induced changes in membrane potential and input resistance that are compatible with GABA(A) receptor activation. Local pressure application of taurine and GABA from a double barrel pipette positioned along the dendritic shaft of pyramidal cells revealed that taurine evoked a very small change of membrane potential and resistance compared with the large changes induced by GABA in these parameters. Moreover, in the presence of GABA(A) antagonists, local application of GABA on the dendrites evoked a GABA(B)-mediated hyperpolarization while taurine did not induce any change. Taurine neither mimicked baclofen inhibitory actions on presynaptic release of glutamate and GABA as judging by the lack of taurine effect on paired-pulse facilitation ratio and slow inhibitory postsynaptic potentials, respectively. These results show that taurine mainly activates GABA(A) receptors located on the cell body, indicating therefore that if taurine has any action on the dendrites it will not be mediated by either GABA(A) or GABA(B) receptors activation.

Taurine-induced synaptic potentiation: role of calcium and interaction with LTP.

Taurine induces a long-lasting potentiation of excitatory synaptic potentials due to the enhancement of both synaptic efficacy and axon excitability in the CA1 area of rat hippocampal slices. In this study, we characterized the role of Ca2+ in the generation of these long-lasting taurine effects. Taurine perfusion in a free-Ca2+ medium did not induce changes in either field excitatory synaptic potentials (fEPSP) slope or fiber volley (FV) amplitude. Intracellular recordings with a micropipette filled with the Ca2+ chelator BAPTA, prevented the EPSP potentiation induced by taurine in the impaled cell, whereas a long-lasting potentiation of the simultaneously recorded fEPSP was obtained. The depletion of intracellular Ca2+ stores by thapsigargin (1 microM), an inhibitor of endosomal Ca2+-ATPase, transformed the taurine-induced potentiation into a transitory process that declined to basal values after taurine withdrawal. Taurine-induced potentiation was not significantly affected by kynurenate (glutamate receptor antagonist), or nifedipine (high-voltage-activated Ca2+ channel antagonist). But, the presence of nickel (50 microM), an antagonist of low-voltage-activated Ca2+ channel, inhibited the taurine-induced potentiation, indicating that Ca2+ influx through this type of Ca2+ channels could account for the Ca2+ requirement of the taurine-induced potentiation. Occlusion experiments between tetanus-induced long-term potentiation (LTP) and taurine-induced potentiation indicate that both processes share some common mechanisms during the maintenance period.