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

Abstract

2. Intravenous injection of galanin (1-6-341 nmol/kg) evoked prolonged attenuation of cardiac vagal action: 409 + 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 sympathetic nerve stimulation. A slight depressor response (-14-4+ 1±9 mmHg) was seen in nine of sixteen cats.3. 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 + 1P7 min. Blood pressure increased by 68-6+557 mmHg.4. Following administration of guanethidine (1 mg/kg i.v.) the inhibitory effect of sympathetic nerve stimulation on cardiac vagal action was significantly reduced (P < 0O001). The responses to exogenous NPY and galanin on vagal action were unchanged after guanethidine.5. The prolonged attenuation of cardiac vagal action can be mimicked by exogenous galanin in the cat but not by exogenous NPY.

Galanin antagonist effects on cardiac vagal inhibitory actions of sympathetic stimulation in anaesthetized cats and dogs.

“…Frequently galanin has been shown to co-exist with classical neurotransmitters and other peptides (Melander L. G. ULAIAN AND OTHERS et al 1985) and interactions between classical transmitters and galanin have been shown in several studies (Fisone et al 1987;Mastropaolo, Nadi, Ostrowski & Crawley, 1988). Revington, Potter & McCloskey (1990), have shown that stimulation of cardiac sympathetic nerves in anaesthetized cats produces a prolonged attenuation of cardiac vagal action. Galanin is known to be co-localized wAith noradrenaline in cardiac sympathetic nerves of the cat (Kummer, 1987) and exogenous galanin produces a similar inhibition of cardiac vagal action in this preparation (Revington et al 1990).…”

“…Revington, Potter & McCloskey (1990), have shown that stimulation of cardiac sympathetic nerves in anaesthetized cats produces a prolonged attenuation of cardiac vagal action. Galanin is known to be co-localized wAith noradrenaline in cardiac sympathetic nerves of the cat (Kummer, 1987) and exogenous galanin produces a similar inhibition of cardiac vagal action in this preparation (Revington et al 1990). On this basis, Revington et al (1990) proposed that the vagal inhibition following cardiac sympathetic stimulation is mediated by the release of endogenous galanin.…”

“…Our study follows on from that of Revington et al (1990). We sought to find out whether galantide could block the effects of exogenous galanin on the cardiac vagus of the anaesthetized cat.…”

“…Galanin is known to be co-localized wAith noradrenaline in cardiac sympathetic nerves of the cat (Kummer, 1987) and exogenous galanin produces a similar inhibition of cardiac vagal action in this preparation (Revington et al 1990). On this basis, Revington et al (1990) proposed that the vagal inhibition following cardiac sympathetic stimulation is mediated by the release of endogenous galanin. Exogenous galanin also produces a fall in systemic blood pressure.…”

“…The right cardiac sympathetic nerve was prepared as described previously by Revington et al (1990) anid was place(d across platinum electrodes for electrical stimulation at 16 Hz (12-15 V, 1 Ins).…”