EFFECT OF PROPRANOLOL ON THE SEROTONIN CONCENTRATION IN THE PORTAL PLASMA AFTER VAGAL NERVE-STIMULATION IN THE CAT

Efferent cervical vagal nerve stimulation in the cat caused a marked increase of the portal plasma 5‐HT concentration. This increase was more than two‐fold within 15 min of stimulation. After cessation of stimulation portal plasma 5‐HT returned to basal levels within 10 min. Treatment with the β‐adrenoceptor antagonist propranolol, in various doses (0.1–2 mg/kg b.wt.), did not abolish but significantly reduced the response to vagal stimulation, particularly during the final part of the stimulation period. The results confirm the existence of a β‐adrenoceptor‐mediated release of 5‐HT, but also suggest that other mechanisms for 5‐HT release may be involved in the response on vagal nerve stimulation. © 1979 Scandinavian Physiological Society