Biphasic Cholinergic Modulation of Reverberatory Activity in Neuronal Networks / 神经科学通报·英文版

Acetylcholine (ACh) is an important neuromodulator in various cognitive functions. However, it is unclear how ACh influences neural circuit dynamics by altering cellular properties. Here, we investigated how ACh influences reverberatory activity in cultured neuronal networks. We found that ACh suppressed the occurrence of evoked reverberation at low to moderate doses, but to a much lesser extent at high doses. Moreover, high doses of ACh caused a longer duration of evoked reverberation, and a higher occurrence of spontaneous activity. With whole-cell recording from single neurons, we found that ACh inhibited excitatory postsynaptic currents (EPSCs) while elevating neuronal firing in a dose-dependent manner. Furthermore, all ACh-induced cellular and network changes were blocked by muscarinic, but not nicotinic receptor antagonists. With computational modeling, we found that simulated changes in EPSCs and the excitability of single cells mimicking the effects of ACh indeed modulated the evoked network reverberation similar to experimental observations. Thus, ACh modulates network dynamics in a biphasic fashion, probably by inhibiting excitatory synaptic transmission and facilitating neuronal excitability through muscarinic signaling pathways.

Efecto de Petiveria alliacea y drogas colinérgicas sobre la habituación / Effects of Petiveria alliacea and cholinergic drugs on the habituation cognitive behavior

Petiveria alliacea (PA) have anxiolytic, antidepressant and cognitive effects. In the present paper the effect of PA water infusion and cholinergic drugs on cognitive behavior were studied. For that, 40 male NMRI mice were divided in 4 groups: Control (n=10), Drug Control (n=10), PA (n=10) and PA plus Drug (n=10). PA 1% was administered orally (7.59±1.39 ml/day); while scopolamine (2 mg/Kg), galantamine (1 mg/Kg) and nicotine (0.1 mg/Kg) were administered intraperitoneally. Behavioral tests included: anxiety maze (AM), open field (OF) and marble burying (MB). Habituation cognitive behavior was evaluated in 4 sessions, one week each session. PA had anxiolytic and antidepressant effect effect in AM, combined with nicotine potentiated an anxiogenic effect in AM, galantamine favored habituation in OF. Scopolamine potentiated the habituation in LA and decreased the obsessive-compulsive behavior in OF. In conclusion; PA had an anxiolytic effect and favored deshabituation, combined with nicotine induced an anxiogenic effect, galantamine favored habituation and scopolamine decreased obsessive-compulsive behavior and favored motor habituation indicated a possible anxiolytic effect.

La Petiveria alliacea (PA) está relacionada con efectos ansiolíticos, antidepresivos y cognitivos. El presente trabajo estudió el efecto de la infusión de PA y drogas colinérgicas sobre la habituación. 40 ratones NMRI machos fueron divididos en 4 grupos: Control (n=10), Control Drogas (n=10), PA (n=10) y PA plus Drogas (n=10). La PA (1%) fue administrada vía oral (7.59±1.39 ml/día); escopolamina (2 mg/Kg), galantamina (1 mg/Kg) y nicotina (0.1 mg/Kg) fueron administrados vía intraperitoneal. Los ensayos conductuales incluyeron: laberinto de ansiedad (LA), campo abierto (CA) y enterramiento aversivo (EA). La habituación fue evaluada en 4 sesiones con duración de una semana cada una. PA mostró un efecto ansiolítico en el LA, combinada con nicotina potenció un efecto ansiogénico en el LA. Galantamina favoreció la habituación en CA, y escopolamina potenció el fenómeno de habituación en LA y disminuyó la conducta obsesivo-compulsiva en CA. En conclusión, la PA mostró un efecto ansiolítico y antidepresivo que potencia la deshabituación, combinada con nicotina indujo un efecto ansiogénico, galantamina favoreció la habituación y escopolamina disminuyó la conducta obsesivo­ compulsiva y favoreció la habituación motora indicando un posible efecto ansiolítico.

Influencia adrenérgica y colinérgica sobre la producción de especies reactivas de oxígeno en neutrófilos humanos* / Adrenergic and cholinergic influence on the production of reactive oxygen species in human neutrophils*

RESUMEN Objetivos. Determinar y comparar el efecto de fármacos agonistas adrenérgicos y colinérgicos sobre la producción de especies reactivas de oxígeno (ROS) en neutrófilos de individuos sanos. Materiales y métodos. Se tomaron muestras de sangre total de cinco participantes para purificar los neutrófilos mediante el método de gelatina. Se midió la producción de ROS por quimioluminiscencia (QLM) usando un contador de centelleo y forbol-12-miristato-13-acetato (PMA) como estímulo. También se realizaron pruebas sin PMA para medir la producción espontánea. Posteriormente, con el mismo método se midió la formación de ROS en presencia de nicotina (agonista colinérgico), salbutamol y clonidina (agonistas adrenérgicos), cada uno en concentraciones de 10-2 M, 10-3 M, 10-4 M y 10-5 M. Se calculó el área integrada bajo las curvas de QLM y se halló el porcentaje de inhibición o de estimulación según sea el caso. Se comparó el efecto provocado por las drogas con sus controles correspondientes y se realizó el análisis estadístico. Resultados. Se obtuvo una disminución de la producción de ROS como efecto de las sustancias estudiadas con una diferencia significativa entre los controles y el efecto producido a 10-2 M, 10-3 M y 10-4 M. Este efecto aumentó de intensidad conforme la concentración de las drogas se incrementó. Los mayores porcentajes de inhibición se mostraron a 10-2 M y 10-3 M. Salbutamol presentó los máximos valores con todas las concentraciones con diferencia significativa entre su inhibición y la generada por las demás drogas. Conclusiones. Los estímulos adrenérgico y colinérgico tienen un efecto inhibitorio de la producción de ROS en neutrófilos de individuos sanos.

ABSTRACT Objectives. To determine and compare the effect of adrenergic and cholinergic agonist drugs on the production of reactive oxygen species (ROS) in neutrophils of healthy individuals. Materials and Methods. Whole blood samples were taken from five participants to purify neutrophils using the gelatin method. The production of chemiluminescent (QLM) ROS was measured using a scintillation counter and phorbol-12-myristat-13-acetate (PMA) as a stimulus. Non-PLA tests were also conducted to measure spontaneous production. Subsequently, with the same method, ROS formation was measured in the presence of nicotine (cholinergic agonist), salbutamol, and clonidine (adrenergic agonists), each in concentrations of 10-2 M, 10-3 M, 10-4 M, and 10-5 M. The area integrated under the QLM curves was calculated and the percentage of inhibition or stimulation was found as the case may be. The effect of the drugs was compared with their corresponding controls and statistical analysis was carried out. Results. A decrease in the production of ROS was obtained as an effect of the substances studied with a significant difference between the controls and the effect produced at 10-2 M, 10-3 M, and 10-4 M . This effect increased in intensity as drug concentration increased. The highest percentages of inhibition were shown at 10-2 M and 10-3 M. Salbutamol presented the maximum values with all the concentrations with a significant difference between its inhibition and that generated by the other drugs. Conclusions. Adrenergic and cholinergic stimuli have an inhibitory effect on the production of ROS in neutrophils of healthy individuals.

Relaxant effects of a hydroalcoholic extract of Ruta graveolens on isolated rat tracheal rings

BACKGROUND: Ruta graveolens L. (R. graveolens) is a medicinal plant employed in non-traditional medicines that has various therapeutic properties, including anthelmintic, and vasodilatory actions, among others. We evaluated the trachea-relaxant effects of hydroalcoholic extract of R. graveolens against potassium chloride (KCl)- and carbachol-induced contraction of rat tracheal rings in an isolated organ bath. RESULTS: The results showed that the airway smooth muscle contraction induced by the depolarizing agent (KCl) and cholinergic agonist (carbachol) was markedly reduced by R. graveolens in a concentration-dependent manner, with maximum values of 109 ± 7.9 % and 118 ± 2.6 %, respectively (changes in tension expressed as positive percentages of change in proportion to maximum contraction), at the concentration of 45 µg/mL (half-maximal inhibitory concentration IC50: 35.5 µg/mL and 27.8 µg/mL for KCl- and carbachol-induced contraction, respectively). Additionally, the presence of R. graveolens produced rightward parallel displacement of carbachol dose-response curves and reduced over 35 % of the maximum smooth muscle contraction. CONCLUSIONS: The hydroalcoholic extract of R. graveolens exhibited relaxant activity on rat tracheal rings. The results suggest that the trachea-relaxant effect is mediated by a non-competitive antagonistic mechanism. More detailed studies are needed to identify the target of the inhibition, and to determine more precisely the pharmacological mechanisms involved in the observed biological effects.

Neurotoxicidade de pesticidas organofosforados durante o desenvolvimento: alterações bioquímicas e comportamentais / Neurotoxicity of organophosphorus pesticides during development: behavioral and biochemical changes

Pesticidas organofosforados são amplamente usados e seu uso constitui um grave problema de saúde pública. A ação clássica destes compostos é a inibição irreversível da acetilcolinesterase, promovendo acúmulo de acetilcolina nas sinapses e hiperestimulação colinérgica. No entanto, as consequências da exposição a baixas doses podem se estender a outros mecanismos de ação e sistemas neurotransmissores. Considerando que crianças constituem um grupo particularmente vulnerável aos efeitos de pesticidas, neste trabalho investigamos os efeitos da exposição aos organofosforados metamidofós (MET) e clorpirifós (CPF) durante o desenvolvimento sobre os sistemas colinérgico e serotoninérgico e sobre o comportamento de camundongos. Para isso, camundongos suíços foram expostos a injeções subcutâneas de MET, clorpirifós ou veículo do terceiro (PN3) ao nono (PN9) dias de vida pós-natal. As doses de exposição foram previamente escolhidas através da construção de uma curva dose-resposta que identificou como mais adequadas para este estudo as doses de 1mg/kg de MET e 3mg/kg de CPF, as quais promoveram em torno de 20% de inibição da acetilcolinesterase. Em PN10, parte dos animais foi sacrificada e foram avaliados os sistemas colinérgico e serotoninérgico no tronco encefálico e córtex cerebral. De PN60 a PN63, os animais foram submetidos a uma bateria de testes comportamentais. Em seguida, estes animais também foram sacrificados tendo sido avaliados os sistemas colinérgico e serotoninérgico. Em PN10, MET e CPF causaram alterações que sugerem aumento da atividade colinérgica respectivamente no tronco e córtex em fêmeas. No sistema serotoninérgico, apenas CPF promoveu alterações, aumentando a ligação ao receptor 5HT1A e transportador 5HT em fêmeas e diminuindo na ligação ao 5HT2. Em PN63, a atividade da acetilcolinesterase foi reestabelecida em todos os grupos. Ainda assim, MET diminuiu a atividade da colina acetiltransferase no córtex e a ligação ao transportador colinérgico.

Organophosphate pesticides are widely used and its use consist on a severe public health problem. The classic effect of these compounds involve irreversible inhibition of the enzyme acetylcholinesterase, causing an accumulation of acetylcholine at cholinergic synapses and, consequently, cholinergic hyperstimulation. However, when the doses of exposure are low, other the mechanisms of action may play a role and other neurotransmitter systems may be affected. Considering that children are particularly vulnerable to effects of these compounds, in this study we investigated the effects of methamidophos and chlorpyrifos organophosphate exposure during development on cholinergic and serotonergic systems and behavior. For this purpose, Swiss mice received subcutaneous injections of methamidophos or chlorpyrifos, or vehicle from the third to the nineth postnatal day (PN3 - PN9). Initially, a dose-response study was performed and the doses of 1mg/kg methamidophos and 3mg/kg chlorphrifos, which promoted 20% inhibition of acetylcholinesterase activity in brain were chosen to be used in the next set of experiments. At PN10, one day after exposure, a group of animals was sacrificed and the brainstem and cortex collected and stored to further analysis of cholinergic and serotonergic systems. From PN60 to PN63 the animals were submitted to behavioral tests in order to evaluate: anxiety, locomotor activity, decision making, depressive-like behavior and learning/memory. After the last test, the animals were sacrificed and the brainstem and cortex collected and stored to further analysis of cholinergic and serotonergic systems. At PN10, methamidophos and chlorpyrifos promoted alterations that suggest an increase of cholinergic activity respectively on the brainstem and cortex of females. As for the serotonergic system: only chlorpyrifos elicited alterations: There were increases in 5HT1A receptor and 5HT transporter binding in females and a decrease in 5HT2 receptor binding.

Histological, biochemical and pharmacologycal characterization of the gastric muscular layer in Chagas disease / Caracterização histológica, bioquímica e farmacológica da musculatura gástrica na doença de Chagas

PURPOSE: To assess in vitro the correlation between the number of neurons and the sensitivity to cholinergic drugs and acetylcholinesterase activity in chagasic patients. METHODS: A 3x1 cm strip of the muscle layer of the anterior part of the stomach, always close to the angular incisure, was removed from 10 chronic chagasic patients (6 men) submitted to megaesophagus or megacolon surgery and from 10 non-chagasic patients (4 men) submitted to other types of surgery (control group), aged on average 52.3 and 50.1 years, respectively, for histological and pharmacological studies. The action of cholinergic drugs was investigated in isolated preparations according to the superfusion method of Ferreira and Costa, and acetylcholinesterase activity was determined by the method of Ellman. For neuron count, the strips were cut into 8 µm sections according to the method standardized by Alcântara. RESULTS: There was a difference in number of neurons between the chagasic (5,6) and control (7,3) groups. Acetylcholinesterase activity, in moles of hydrolyzed substrate per minute per gram tissue, was reduced in chagasic patients (4,32) compared to the controls (7,30). No hypersensitivity of the gastric musculature to cholinergic drugs was detected, with a reduced maximum response to carbachol and betanechol in the chagasic group. CONCLUSIONS: The reduction of neurons in the myenteric plexus of the stomach of chronic chagasic patients can be demonstrated even in the absence of clinical chagasic gastropathy. The hypersensitivity of the gastric musculature to cholinergic drugs probably depends on intense denervation. The reduced acetylcholinesterase activity demonstrates the involvement of the cholinergic innervation in the stomach of chronic chagasic patients. There was no correlation between number of neurons, sensitivity to cholinergic drugs and acetylcholinesterase activity in the gastric musculature of chagasic and non-chagasic patients.

OBJETIVO: Avaliar in vitro a correlação entre o número de neurônios e a sensibilidade a drogas colinérgicas e a atividade da acetilcolinesterase em pacientes chagásicos. MÉTODOS: Em 10 pacientes chagásicos crônicos (6 homens) submetidos à cirurgia de megaesôfago ou de megacólon e em 10 pacientes não chagásicos (4 homens) submetidos a outros tipos de cirurgia (grupo controle), respectivamente com idade média de 52,3 e 50,1 anos, retirou-se uma tira de 3x1 cm da camada muscular da parede anterior do estômago, sempre junto á cisura angular, que serviu para os estudos histológicos e farmacológicos. A ação de drogas colinérgicas foi feita em preparação isolada de acordo com o método de superfusão de Ferreira e Costa, e a determinação da atividade da acetilcolinesterase pelo método de Ellman. Para a contagem de neurônios a tira muscular foi submetida a cortes de 8 micra segundo método padronizado por Alcântara. RESULTADOS: Houve diferença do número de neurônios entre os grupos chagásico (5,6) e controle (7,3). A atividade da acetilcolinesterase mostrou-se diminuída nos chagásicos (4,32) expressa como número de moles do substrato hidrolisado por minuto por grama de tecido, em relação aos controles (7,30). Não se encontrou hipersensibilidade da musculatura gástrica a drogas colinérgicas, encontrando-se inclusive efeito máximo reduzido ao carbacol e betanecol no grupo chagásico. CONCLUSÕES: A redução de neurônios no plexo mioentérico do estômago de pacientes chagásicos crônicos pode ser demonstrada mesmo na ausência de gastropatia chagásica clínica. A hipersensibilidade da musculatura gástrica a drogas colinérgicas provavelmente depende de desnervação intensa. A redução da atividade da acetilcolinesterase demonstra o comprometimento da inervação colinérgica no estômago de pacientes chagásicos crônicos. Não houve correlação entre número de neurônios, sensibilidade a drogas colinérgicas e atividade da acetilcolinesterase na musculatura gástrica de pacientes chagásicos ou não chagásicos.

Curso temporal dos efeitos da exposição combinada de nicotina e etanol no sistema colinérgico cerebral durante adolescência / Time course of the effects of combined exposure to nicotine and ethanol in the brain cholinergic system during adolescence

O etanol e a nicotina são as drogas mais comumente usadas no mundo. Como claramente indicado por estudos epidemiológicos, existe uma forte associação entre o tabagismo e o consumo de etanol principalmente durante o período da adolescência. Entretanto, existem poucos estudos em neurobiologia básica que avaliem o efeito da exposição combinada de nicotina e etanol durante o período da adolescência. Considerando que a nicotina é um agonista do receptor colinérgico nicotínico (nAChR) e que tem sido demonstrado que o etanol interage com os nAChRs, o presente trabalho tem como foco o estudo dos efeitos da exposição à nicotina e/ou ao etanol no sistema colinérgico durante a adolescência. Do 30º ao 45º dia pós-natal (PN) camundongos da cepa C57BL/6 foram expostos à nicotina (NIC) e/ou etanol (ETOH). Quatro grupos foram analisados: 1) exposição concomitante (NIC+ETOH) à solução de nicotina (50ug/ml) e etanol (25%, 2g/kg i.p. em dias alternados), 2) exposição a NIC, 3) exposição ao ETOH, 4) exposição ao veículo. Foram quantificadas a expressão/afinidade do [3H] hemicolinium-3 (HC-3) ao transportador de alta afinidade présinaptico de colina, ao final da exposição (PN45), após curto (PN50) e longo período de retirada (PN75). Ao final da exposição, o grupo NIC+ETOH apresentou upregulation de nAChRs, refletindo simples somação dos efeitos da NIC e ETOH no córtex cerebral e sinergismo no mesencéfalo. A upregulation devido à exposição combinada foi mantida mesmo após alguns dias de retirada das drogas. Um mês após o término da exposição, os valores foram semelhantes aos obtidos para os animais veículo. Em PN45, machos NIC apresentaram aumento da ChAT no córtex cerebral, mas o ETOH foi capaz de reverter este efeito. Ao contrário, fêmeas NIC apresentaram diminuição da ChAT. No mesencéfalo, somente ETOH promoveu aumento da ChAT. Já em PN50, o grupo NIC apresentou aumento na ChAT que foi revertido na retirada combinada de NIC+ETOH. Em PN75, o grupo NIC+ETOH...

Nicotine and ethanol are the most commonly consumed drugs. As clearly indicated by epidemiological studies, there is a close interrelationship between smoking and alcohol consumption manly during adolescence period. However, there are few studies on the basic neurobiology of the effects of the combined nicotine and ethanol exposure in the adolescent brain. Since nicotine is a cholinergic agonist and it has been shown that ethanol interferes with nicotinic acetylcholine receptors (nAChR), the current proposal will focus on the cholinergic effects of nicotine and/or ethanol treatment during adolescence. From the 30th to the 45th postnatal day (PN), C57BL/6 mice were exposed to nicotine free base (NIC) and/or ethanol (ETOH). Four groups were analyzed: 1) concomitant (NIC+ETOH) exposure of nicotine (50 ug/ml) and ethanol (25%, 2 g/kg i.p. every other day); 2) NIC exposure; 3) ETOH exposure; 4) vehicle. We assessed nAChR (alfa4beta2) binding, choline acetyltransferase (ChAT) activity and [3H] hemicholinium-3 (HC-3) binding to the high affinity presynaptic choline transporter at the end of exposure period (PN45), at short (PN50) and long term (PN75) withdrawal. At the end of exposure period, NIC+ETOH elicited a pronounced upregulation which reflect simple additivity of the effects of nicotine and ethanol in the cerebral cortex and synergism in the midbrain. On PN45, male NIC mice presented an increase in ChAT in the cerebral cortex. However, ETOH reversed this effect. In contrast, female NIC mice presented decreased ChAT activity. In the midbrain, ETOH increased ChAT. On PN50, NIC mice presented an increase in ChAT activity that was reversed by ETOH withdrawal. In addition, NIC+ETOH long term withdrawal elicited a decrease in ChAT activity. Regarding HC-3, binding was not affected on PN45. ETOH and NIC+ETOH withdrawal promoted a decrease at short and long-term withdrawal. These results provide experimental evidences that nicotine and ethanol during adolescence...

Effect of KATP channel openers on myogenic and neurogenic responses in goat urinary bladder.

Isolated goat detrusor muscle exhibited spontaneous contractility with an irregular amplitude and frequency. The spontaneity of detrusor muscle exhibited a mean amplitude as 11.99 +/- 0.83 mm and frequency as 1.37 +/- 0.16/min. KATP-channel openers namely, cromakalim or pinacidil (10(-7) - 10(-4) M) added cumulatively, elicited a concentration-related inhibition of both amplitude and rate of spontaneous contractions. The mean IC50 values for both amplitude and frequency for cromakalim were 3.3 x 10(-6) M and 2.9 x 10(-6) M, respectively; and for pinacidil were 2.0 x 10(-5) M and 1.5 x 10(-5) M, respectively. Glibenclamide, a KATP-channel blocker inhibited the cromakalim-induced concentration-related relaxation of spontaneous contractions with a significant increase in its mean IC50. ACh-induced concentration-related contractile response was inhibited in the presence of either cromakalim (10(-4) M) or pinacidil (10(-4) M). The mean EC50 value of ACh, in the presence of cromakalim (2.5 x 10(-3) M) was significantly increased as compared to the control (1.2 x 10(-6) M). In the presence of glibenclamide (10(-5) M) the inhibitory effect of cromakalim was significantly reduced with consequent decrease in the EC50 value (1.9 x 10(-5) M). Application of EFS (30 V and 5 ms) on goat urinary bladder strips at 1, 2, 5, 10, 20 and 30 Hz elicited frequency-related contractile responses. Both cromakalim and pinacidil caused a rightward shift in the frequency-related contractile response curve with significant increase in the mean EF25 and EF50 values, respectively. In the presence of glibenclamide (10(-4) M), the frequency-related inhibitory response curve was shifted to left with significant (P < 0.001) increase in the mean EF25, EF50 and EF75. The present results suggest that in the goat detrusor muscle, agonist and EFS-induced contractile responses were more potently inhibited by cromakalim than pinacidil with activation of glibenclamide sensitive KATP channels.

Lead acetate induced contraction in rat tracheal smooth muscle is independent of epithelium.

Airways are the primary target of lead exposure from atmospheric pollution, its effect on airway smooth muscle and their responsiveness to bronchoactive agents is not clearly understood. In the present investigation the effect of lead on the isolated airway smooth muscle activity was studied in organ bath set-up. Further the involvement of airway epithelium was examined and the responsiveness of airway smooth muscle to adenosine, acetylcholine (bronchoconstrictors) and isoproterenol (bronchodilator) was also investigated. Lead in concentration of 10(-12) M to 10(-4) M produced concentration-dependant contractile response in rat tracheal rings. Acetylcholine and adenosine induced concentration-dependent contractile response was slightly inhibited after lead exposure. The relaxant response to isoproterenol was also inhibited in lead exposed tissues. Epithelium removal did not significantly change the contractile response to lead suggesting that the lead induced contraction of airway smooth muscle is epithelium independent.

Intervención colinérgica en la enfermedad de Alzheimer y otras manifestaciones neuropsiquiátricas / Cholinergic intervention in Alzheimerïs disease and other neuropsychiatric manifestations

Las neuronas colinérgicas del telencéfalo basal suministran una profusa inervación a toda la corteza cerebral, constituyendose en el principal sistema modulador de la actividad cortical, participando en la regulación del estado de alerta y la atención. La denervación colinérgica, secundaria a la degeneración de estas neuronas en la enfermedad de Alzheimer, se relaciona directamente con el desarrollo de los síntomas de enfermedad, lo que ha impulsado la búsqueda de diversas formas de suplir la deficiencia de acetilcolina en la corteza. Hasta ahora los inhibidores de la acetilcolinesterasa han entregado los mejores resultados, pero estos no han sido más que modestos. En la presente revisión se examinan las bases fisiológicas y fisiopatológicas que avalan la intervención sobre el sistema colinérgico central y se examinan los resultados registrados en la enfermedad de Alzheimer y su extensión hacia otras manifestaciones neurosiquiátricas. Finalmente, se hace enfásis en que tratandose de una enfermedad degenerativa, lo más trascendente no es la disminución de un neurotransmisor, sino la perdida de las neuronas que los secretan y la interrupción de los circuitos en que estas neuronas participan

Mechanism of UV light-induced photorelaxation in isolated rat aorta

Isolated rat thoracic aorta which is pharmacologically precontracted by phenylephrine induces photorelaxation when exposed to long wave length UV-light. The aim of the present study was to characterize the mechanism of UV-light induced by photorelaxation in the rat aorta. 1. UV light relaxed both endothelium-intact and -denuded rat aortic rings contracted by phenylephrine. The magnitude of relaxation on UV light was dependent on the exposure time and slightly greatly in endothelium-denuded rings than in endothelium-intact preparations. 2. L-NAME (10 nM-100 uM) but not D-NAME completely inhibited the photorelaxation in a concentration dependent manner. 3. The UV-induced relaxation was inhibited by methylene blue (1 -100 uM), and verapamil (100 nM), and removal of extracellular Ca2+. In contrast, UV-light induced photorelaxation was potentiated by N(w)-nitro-Larginine (L-NOARG) treatment. 4. In immunocytochemical analysis of UV-light induced iNOS and eNOS expression in rat aortas, at which expression levels were increased in a time-dependent manner on UV-irradiation in aortic endothelium and smooth muscle, respectively. These results suggest that UV light-induced photorelaxation may be due to nitric oxide from exogenously administered L-arginine as well as endogenous nitric oxide donors such as amino acid and arginine derivatives. Additional suggestion is that UV light stimulates the expression of nitric oxide synthases, and its activity for nitric oxide generation is dependent on cytosolic Ca2+ originated from extracellular space.

Resting and reflex heart rate responses during cholinergic stimulation with pyridostigmine in humans

Dysfunction of the autonomic nervous system is of prognostic value for sudden death after acute myocardial infarction. Although the use of beta-blockers to counteract the adrenergic hyperactivity has been shown to decrease mortality in these patients, there have been no reports on the role of cholinomimetic drugs in the prognosis of patients after myocardial infarction. The present study was designed to investigate the effect of the administration of pyridostigmine bromide, a reversible anti-cholinesterase agent, on cardiac cholinergic activity assessed by the resting and reflex heart rate responses. Eight healthy volunteers were submitted to a conventional 12-lead electrocardiogram to obtain resting heart rate, and to three non-invasive cardiovascular tests: respiratory sinus arrhythmia, Valsalva maneuver and 4-sec exercise test. On two different days and following a randomized crossover double-blind protocol, the experiments were performed before and 120 min after oral administration of either pyridostigmine bromide (30 mg) or placebo. Pyridostigmine increased (P<0.05) the duration of the R-R intervals at rest (pre: 898 ñ 30 msec; post: 1019 ñ 45 msec; pre-placebo: 916 ñ 26 msec; post: 956 ñ 28 msec; P>0.05). Although the duration of the R-R intervals during the autonomic tests was also increased (P<0.05), the derived indexes of maximal fluctuation during the maneuvers did not change. These results indicate that oral pyridostigmine produces tonic cardiac cholinergic stimulation while exerting no effect on its reflex changes. Further studies are needed to address the potential role of the administration of pyridostigmine in the prognosis of patients with acute myocardial infarction.

Acción anticolinérgica de clonidina sobre los efectos cardiovasculares de la estimulación colinérgica central / Anticholinergic action of clonidine on cardiovascular effects of the central cholinergic estimulation

Fue realizado un estudio acerca de la acción anticolinérgica del agonista adrenérgico alfa2 clonidina sobre las respuestas cardiovasculares a la inyección i.c.v. del agente anticolinesterásico cuaternario neostigmina a ratas conscientes. E1 agente colinérgico neostigmina (0,1-1 mug i.c.v.) indujo en las ratas una respuesta presora y bradicardia en forma dependiente de la dosis. Clonidina, a la dosis de 10 mug. Kg(-1) (i.v.) y administrado 30 min antes del anticolinesterásico, no modificó el efecto presor de neostigmina (0,1-1 mug i.c.v.) pero previno la bradicardia. Por otra parte, la administración i.c.v. de clonidina (3 mug), inyctada 15 min. antes de neostigmina, sólo previno el efecto bradicardizante del anticolinesterásico (0,3 mug i.c.v.) pero la acción presora central de la droga. Estos resultados sostienen la idea de que la clonidina tiene una acción anticolinérgica en la rata. Sin embargo, la prevención por clonidina de la bradicardia inducida por estimulación central sugiere una interacción diferente colinérgica-adrenérgica según la respuesta cardiovascular originada por la administración central de agentes colinérgicos. .

La activación muscarínica del músculo liso de las vías aéreas / The muscarinic activation of smooth muscle of airway

La activación de receptores muscarínicos del músculo de las vías aéreas provoca la generación de varios segundos mensajeros (AMPc e GMPc e IP3). La activación del receptor muscarínico M3 producida por el carbacol induce a incrementos significativos en los segundos mensajes antes mencionados. Después de la adición de carbacol, una cinética diferente fue encontrada para estos segundos mensajeros. El IP3 mostró un primer pico (10 seg), el cual precede el inicio de la contracción muscular lisa. Además, un segundo pico de este segundo mensaje de inositol fue detectado a los 60 segundos. Con respecto a los nucleótidos ciclicos, el AMPc mostró un solo pico a los 20 segundos y el GMPc mostró la existencia de dos picos. Así, este último nucleótico mostró un primer pico a los 20 segundos, el cual coincide con el pico de AMPc y un segundo pico a los 60 segundos, después que la contracción muscular lisa se estabilizó. El último pico parece ser sensible a los atrapadores de grupos NO como es el azul de metileno, sugiriendo a la guanililciclasa soluble como la enzima responsable de este segundo pico. Adicionalmente; el KCL es capaz de inducir la contracción del músculo liso que parece ser diferente en varios aspectos a la activación muscarínica del músculo liso de las vías aéreas