Prolonged inhibition of cardiac vagal action following sympathetic stimulation and galanin in anaesthetized cats.

Publisher Website
Google Scholar
Abstract
Stimulation of the right cardiac sympathetic nerve for 3 min at 16 Hz in the presence of effective .beta.-adrenoceptor blockade evoked prolonged attenuation of cardiac vagal action in the cat: 40.8 .+-. 5.4% maximum inhibition of cardiac vagal action on prolonging pulse interval, with half-time to recovery of 8.3 .+-. 1.4 min. Intravenous injection of galanin (1.6-3.1 nmol/kg) evoked prolonged attenuation of cardiac vagal action: 40.9 .+-. 8.2% maximum inhibition with a half-time to recovery of 13.6 .+-. 2.6 min. This effect of galanin was not significantly different from the action of symapthetic nerve stimulation. A slight depressor response (-14.4 .+-. 1.9 mmHg) was seen in nine of sixteen cats. Intravenous injection of neuropeptide Y (NPY) (2.8-6.3 nmol/kg) evoked slight attenuation of cardiac vagal action: 11.9 .+-. 4.5% maximum inhibition of cardiac vagal action on pulse interval, with a half-time to recovery of 4.1 .+-. 1.7 min. Blood pressure increased by 68.6 .+-. 5.7 mmHg. Following administration of guanethidine (1 mg/kg I.V.) the inhibitory effect of sympathetic nerve stimulation on cardiac vagal action was significantly reduced (P < 0.001). The response to exogenous NPY and galanin on vagal action were unchanged after guanethidine. The prolonged attenuation of cardiac vagal action can be mimicked by exogenous galanin in the cat but not by exogenous NPY.