Effects of clorgyline on the release of noradrenaline from rat vas deferens

Abstract

Release of endogenous noradrenaline (NA) and functional activity of presynaptic α 2-adrenoceptors were measured in isolated rat vas deferens following acute (2 mg/kg) or chronic (21 ∗ 1 mg/kg daily, i.p.) treatment with clorgyline. Noradrenaline tissue content was higher in rats treated chronically with clorgyline than in those treated acutely. In vitro experiments done in the presence of 1 μM desipramine and 0.5 μM yohimbine showed that NA release, elicited by electrical field stimulation, was higher in chronic clorgyline rats than in controls, while no significant difference was found between acute clorgyline and control rats. Yohimbine enhanced evoked release of NA in all treatment groups, provided that desipramine was present in the Krebs solution, and the enhancement was non significantly higher in chronic clorgyline than in acute clorgyline and control rats. Efflux of 3,4-dihydroxyphenylglycol was lower in chronic clorgyline rats than in other groups. No difference was found between the treatment groups in a 1 min [ 3H]NA uptake into the tissue, nor in the ability of desipramine (1 μM) to block the uptake. The results indicate that following chronic treatment with clorgyline, evoked release of NA increased, and there was no reduction in the ability of the presynaptic α 2-adrenoceptor inhibitory mechanism to reduce nerve stimulation induced release of NA.