RESUMO
The influence of drugs affecting different neurotransmitter systems on an acute abstinence head-shaking (AHS) model induced by nalorphine or naloxone was studied in 9-day-old rat pups pretreated (3 h before) with morphine (10 mg/kg, i.p.). One hour after the injection of nalorphine (10 mg/ kg, i.p.) AHS was stopped by a second dose of morphine (10 mg/kg, i.p.) and reinitiated 1 h later by a higher dose of nalorphine (20 mg/kg, i.p.). In other groups AHS was blocked by spiroperidol (0.1 mg/kg, i.p.), clonidine (0.01 mg/kg, i.p.) or scopolamine (50 mg/kg, i.p.). In these groups a second injection of nalorphine did not reinitiate AHS. In dose-effect curve experiments the AHS induced by naloxone or nalorphine was significantly reduced by previous injections of scopolamine, spiroperidol, metergoline or phentolamine in the corresponding groups. Scopolamine was the only antagonist which displaced the AHS dose-effect curves to the right without affecting the maximal response. Since no common receptors exist for a direct competitive interaction between opiate antagonists and scopolamine, these experiments suggest that a direct molecular relationship exists between the tissue concentration of nalorphine (or naloxone) and the endogenous ACh release during abstinence. Thus, the AHS model in 9-day-old rats clearly differentiates specific from non-specific blockade of the abstinence syndrome, and confirms a distinct or primary role of cholinergic neurotransmission in morphine abstinence.
Assuntos
Acetilcolina/fisiologia , Cabeça/fisiologia , Dependência de Morfina , Movimento/efeitos dos fármacos , Antagonistas de Entorpecentes/efeitos adversos , Transmissão Sináptica/efeitos dos fármacos , Animais , Animais Recém-Nascidos , Ratos , Ratos WistarRESUMO
Serotonin (5-HT) effects on physostigmine (PHY)-induced yawning were studied in LY Sprague-Dawley rats by injecting Lu 10 171 (citalopram), a specific 5-HT uptake blocker, and two antagonists--methiothepine and ritanserin--which differ slightly in the selectivity of their actions on different 5-HT receptor subtypes. Infant and young rats show significant increases in PHY-induced yawning when preinjected with citalopram (5-10 mg/kg). Two-month-old animals show this effect only with 10 mg/kg. With adult animals (3-5 months old), the effect is the opposite: Yawning decreases. The facilitory effect in infant and young rats was counteracted by methiothepine but not by ritanserin, suggesting that it is mediated through 5-HT1A or 5-HT1B receptor subtypes. The inhibitory effect of citalopram in adult rats was unmodified by the two antagonists used, leaving open the possibility that it is mediated by 5-HT3 receptors.
Assuntos
Envelhecimento/psicologia , Serotonina/fisiologia , Bocejo/fisiologia , Animais , Citalopram/farmacologia , Masculino , Metiotepina/farmacologia , Fisostigmina/farmacologia , Ratos , Ratos Sprague-Dawley , Ritanserina/farmacologia , Antagonistas da Serotonina/farmacologiaRESUMO
The electroencephalographic sleep patterns recorded during short periods of time (3 h) of a neurological mutant rat (taiep) were studied. This rat exhibits, among other signs, immobility episodes that are similar to those observed in narcolepsy-cataplexy. We describe findings of long term (6 months) electroencephalographic studies done in 9 mutant and 5 control rats. The mutant rats present electroencephalographic and behavioral disorders consisting of: (a) bursts of cortical waxing and waning waves occurring during the drowsy state; in some animals this activity represents up to 25% of the total drowsiness time; (b) shortened sleep time; (c) fragmented paradoxical sleep; (d) immobility episodes when the animals are subjected to an emotional excitement; and (e) electrographic activity of paradoxical sleep without atonia during the immobility episodes. These findings show that the taiep mutant shows several aspects of narcolepsy-cataplexy and it may represent an experimental model for the study of this pathology.
Assuntos
Cataplexia/fisiopatologia , Modelos Animais de Doenças , Eletroencefalografia , Transtornos dos Movimentos/fisiopatologia , Narcolepsia/fisiopatologia , Animais , Cataplexia/genética , Feminino , Masculino , Transtornos dos Movimentos/genética , Narcolepsia/genética , Ratos , Ratos Mutantes , Sono/fisiologia , Fases do Sono , Sono REM/fisiologia , VigíliaRESUMO
The hypothetical modulation by GABAergic neurons of yawning behavior in the rat was explored with GABA-active drugs. Gamma-acetylenic-GABA, a specific inhibitor of GABA-T, increases yawning frequency when injected at a dose of 7 mg/kg. Baclofen, a GABAB agonist (3 mg/kg), inhibits yawning completely; GABA antagonists, bicuculline and picrotoxin, at subconvulsant doses, also decrease yawning. All drugs were injected intraperitoneally with the exception of apomorphine, which was injected subcutaneously. It is suggested that GABAB receptors play a role in yawning behavior by modulating ACh release, and that GABAA receptors may modify yawning frequency by modulating inhibitory influences on ACh neurons.