Abstract

The effects of nicotine on gastric antral and duodenal contractile activity were determined in dogs chronically implanted with strain gauge force transducers. Nicotine, 25 to 100 µg/kg i.v., produced an inhibition of contractile activity of circular and longitudinal muscle in both the gastric antrum and the duodenum. The inhibition was immediate in onset, and was neither preceded nor followed by a stimulation of contractile activity. The magnitude and duration of inhibition were proportional to the dose. Contractile activity during both the digestive and interdigestive states was inhibited by nicotine. The inhibitory response was essentially unchanged after repetitive administration of nicotine every ½ hour for 24 hours. Intravenous administration of other ganglionic stimulants (dimethyiphenylpipemazinium, AHR-0602 and McN A-343) as well as epinephrine and norepinephrine produced an inhibition of contractile activity similar to that produced by nicotine. Pretreatment with reserpine abolished the inhibitory effect of nicotine. Pretreatment with tolazoline reduced the inhibitory effect of nicotine, epinephrine and norepinephrine, whereas the following had no effect on response to nicotine and the catecholamines: phenoxybenzamine, dihydroergotamine, dl-propranolol and phenoxybenzamine in combination with dl-propranolol. It was concluded that nicotine produces inhibition of gastric antral and duodenal contractile activity by activation of adrenergic inhibitory systems.