The effect of propranolol on the serotonin concentration in the portal plasma after vagal nerve stimulation in the cat

Abstract

Efferent cervical vagal nerve stimulation in the cat caused a marked increase of the portal plasma 5-HT [serotonin] concentration. This increase was more than 2-fold within 15 min of stimulation. After cessation of stimulation, portal plasma 5-HT returned to basal levels within 10 min. Treatment with the .beta.-adrenoceptor antagonist propranolol in various doses (0.1-2 mg/kg body weight) 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 .beta.-adrenoceptor-mediated release of 5-HT, but suggest that other mechanisms for 5-HT release may be involved in the response on vagal nerve stimulation.