NEUROGENIC INHIBITION OF DUODENAL AND JEJUNAL MOTILITY IN THE ANESTHETIZED RAT

Duodenal or jejunal motility (monitored as pressure changes in a saline-perfused intraluminal catheter) was studied in anaesthetized rats, vagotomized and pretreated with adrenergic blocking agents. In the duodenum (but not the jejunum), atropine or the selective muscarinic M(1) and M(3) receptor antagonists, pirenzepine and 4-diphenyl-acetoxy-N-methylpiperidine (4-DAMP), respectively, augmented the spontaneous contractile activity. This effect could be abolished either by nicotinic ganglionic receptor antagonism with hexamethonium, or with morphine. Moreover, blockade of the synthesis of nitric oxide by N-omega-nitro-L-arginine elicited hypermotility both in the duodenum and the jejunum, and also this response was abolished by hexamethonium. It is proposed from the present results that the rat small intestine is controlled by non-adrenergic, non-cholinergic inhibitory as well as excitatory motor neurons. The latter motor neurons seem to be modulated by muscarinic, nitroxergic or opioidergic mechanisms.