Abstract
Summary
Analyzing the mechanism of thermal reaction, we found that exogenous K+ potentiates cold contraction in rat intestine (or vas defenens) but has no similar effect on guinea pig intestine. A dibenzazepine, Protriptyline, which slightly relaxes the vas deferens of rat, induces a high potentiation of the contractions by thermal stimulus, K+, and norepinephrine. Norepinephrine contraction is not modified by thermal stimulation or K+. Reserpine is species specific on the isolated intestine: it abolishes cold contraction in guinea pig, while in rats only the spontaneous movements are decreased. However, the thermal response of the intestine in both species is inhibited by in vivo reserpinization. Cooling of guinea pig intestine in presence of reserpine increases K+ release, a mechanism which may be responsible for some of its toxic action on contracting organs, such as the cardiac insufficiency in rats accompanied by K+ release 9 and in patients treated with cardiac glycosides and reserpine 10 .
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