Effects of ionic alterations on various sympathetic nerve-smooth muscle preparations.

Abstract

SummaryIsolated preparations of guinea pig, rat and rabbit vas deferens, and Finkleman preparations of rabbit ileum and rat and guinea pig colon have been used to study the effects of ionic alterations on responses to added noradrenaline and to stimulation of sympathetic nerves. With vas deferons preparations it was found that, depending on the species used, these responses were affected differently by certain of the ionic alterations. Intestinal preparations from the three species behaved more consistently.Species difierences in vas deferens preparations were seen in response to the following ionic changes: (i) reduction in sodium chloride (replaced by sucrose); (ii) absence of potassium; (iii) increasing potassium to 15 and 20 mM, and (iv) raising calcium to 5–10 mM. Lowering calcium to 0·25–0·5 mM depressed the responses of vas deferers from all three species.Intestinal preparations showed a uniform depression in 7·5–10 mM calcium. Raised potassium depressed the response to sympathetic nerve stimulation in all three species, though the response to noradrenaline was affected differently with different species.The interactions of drugs and ions also showed differences with the three species. While 15 mM potassium could reverse the blocking action of both guanethidine and procaine on guinea pig vas deferens, it was almost ineffective on rat vas deferens, and on intestinal preparations raised potassium increased the blocking action of these drugs. High calcium, which enhanced the effects of sympathetic nerve stimulation in varions tissues, failed to modify the blocking action of guanethidine.