Central inhibition of gastric motility by intravenously administered nicotine in rats.
Effects of intravenously (i.v.) administered nicotine on gastric motility were investigated in urethane-anesthetized rats in which an intragastric balloon had been placed. I.v. administered nicotine at 75-300 nmole/kg dose-dependently decreased gastric motility. Decrease in gastric motility induced by nicotine at the dose of 300 nmole/kg was inhibited by intracisternally administered hexamethonium. Gastric motility was also decreased by intracisternally applied nicotine (1-10 nmole). These doses were much smaller than those by the intracerebroventricular route in our previous report. Bilateral vagotomy significantly suppressed basal gastric motility. In bilaterally vagotomized animals, nicotine at 1 mumole/kg but not 300 nmole/kg given i.v. significantly decreased the gastric motility maintained at a normal level by electrical stimulation of the vagus nerve. This nicotine-induced decrease in gastric motility, under conditions of electrical stimulation of the vagus nerve, was inhibited by pretreatment with phentolamine. These results suggest that a smaller dose of nicotine given i.v. activates nicotinic receptors in the brainstem and elicits vagally-mediated inhibition of gastric motility. Activation of peripheral alpha-adrenergic mechanisms together with that of central nicotinic mechanisms may be involved in the decreasing effects of a larger dose of nicotine on gastric motility.
Nagata
M
M
Department of Pharmacology, Kochi Medical School, Japan.
Osumi
Y
Y
D000758:Anesthesia; D000818:Animals; D001933:Brain Stem / Q000502:physiology; D002946:Cisterna Magna; D005769:Gastrointestinal Motility / Q000187:drug effects*; D006584:Hexamethonium Compounds / Q000494:pharmacology; D007267:Injections; D007275:Injections, Intravenous; D008297:Male; D009538:Nicotine / Q000008:administration & dosage / Q000494:pharmacology*; D010646:Phentolamine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D014628:Vagotomy
D006584:Hexamethonium Compounds; D009538:Nicotine; D010646:Phentolamine