Role of M1 muscarinic receptors in the parasympathetic control of colonic motility in cats and rabbits.
AUTOR(ES)
Blanquet, F
RESUMO
1. The effects of pirenzepine (a selective blocking agent of M1 muscarinic receptors) were studied on excitatory junction potentials (EJPs) and inhibitory junction potentials (IJPs) elicited on colonic smooth muscle by stimulation of efferent parasympathetic nerve fibres in anaesthetized cats and rabbits. 2. Pirenzepine (25 micrograms kg-1 to 0.2 mg kg-1, i.v.) decreased the amplitude of EJPs or abolished them. In pirenzepine, parasympathetic stimulation elicited IJPs in most cases. 3. In both species, pirenzepine initiated spontaneous IJPs, indicating an increase in the activity of the non-adrenergic, non-cholinergic (NANC) inhibitory neurones. 4. The results suggest that M1 muscarinic receptors are involved in synaptic transmission within intramural plexuses, at interneuronal synapses in the parasympathetic excitatory pathway to colonic smooth muscle, but are not involved in the pathway to the NANC inhibitory neurones. The facilitation of IJPs by pirenzepine suggests that, under normal physiological conditions, NANC neurones are tonically inhibited by an intramural nervous circuit involving M1 muscarinic receptors.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1175177Documentos Relacionados
- Colonic motility and transit of digesta during hard and soft faeces formation in rabbits.
- Role of motility in experimental cholera in adult rabbits.
- Age-dependent decrease in the affinity of muscarinic M1 receptors in neocortex of rhesus monkeys.
- M1 and M2 muscarinic receptors mediate excitation and inhibition of guinea-pig intracardiac neurones in culture.
- Cloned M1 muscarinic receptors mediate both adenylate cyclase inhibition and phosphoinositide turnover.