Studies of reflex activity in involuntary nervous system: II. Action of ergotamine on vaso-motor reflexes

Altered adrenergic activity in coronary arterial spasm: insight into mechanism based on study of coronary hemodynamics and the electrocardiogram

To elucidate the pathophysiologic mechanism of coronary arterial spasm, the hypothesis was examined that underlying alterations in sympathetic activity may account for this syndrome in some patients. Observations were directed to alterations in coronary arterial hemodynamics and the electrocardiogram. Spasm of the left anterior descending coronary artery produced a mean increase in coronary vascular resistance of 107 percent (P less than 0.05) in four patients in whom coronary sinus blood flow was measured with the thermodilution technique. The alpha adrenergic blocking agent phentolamine, given intravenously, acutely reversed coronary spasm and its clinical manifestations in eight patients and reduced coronary resistance. In four patients, administration of the long-acting oral alpha blocking agent phenoxybenzamine (20 to 80 mg/day) caused disappearance of symptoms during a follow-up period of 3 to 12 months. Transient prolongation of the corrected Q-T interval preceded spontaneous or ergonovine maleate-provoked coronary spasm in 11 patients with variant angina pectoris, whereas no significant change in the Q-T interval followed ergonovine administration in 27 control patients with atypical chest pain who did not have coronary spasm. T wave inversions in the resting electrocardiogram were normalized by isoproterenol infusion in one patient and by long-term phenoxybenzamine treatment in four patients with variant angina pectoris. These Q-T and T wave changes are analogous to those described with unilateral or asymmetric stellate ganglion stimulation in animals. These observations suggest that alterations in the sympathetic nervous system that are consistent with asymmetric stellate ganglion activity and transient alpha adrenergic receptor stimulation can presage the development of coronary arterial spasm in some patients with variant angina pectoris.

Depression and enhancement of baroreceptor pressor response in cats after intracerebroventricular injection of noradrenergic blocking agents: dependence on supracollicular areas of the brain

The alpha-adrenergic blocking drugs, phentolamine and Hydergine, both act centrally at different sites to depress and enhance the pressor and sympathetic nerve response to decreased baroreceptor afferent input in anesthetized cats. Depression of the rise in blood pressure and sympathetic nerve discharge during bilateral carotid occlusion (BCO) followed injection of the agents into the 4th cerebral ventricle when the brain was intact but not when connections were interrupted at the midcollicular level by transection or lesion. Enhancement of responses occurred when drug distribution was confined to the brain rostral to the midcollicular level via injection into the 3rd cerebral ventricle with the cerebral aqueduct cannulated. Both agents decreased resting blood pressure and Hydergine decreased heart rate in intact and decerebrate preparations but not in 3rd ventricle-cerebral aqueduct experiments. We found that pretreatment with the noradrenergic precursor. L-dopa consistently prevented depression by phentolamine but was less effective against Hydergine. The results indicate that mechanisms which enhance and suppress the baroreceptor pressor response are normally operative in anesthetized cats and, furthermore, that neural pathways mediating the effects are ones connecting the caudal brainstem with supracollicular levels of the brain. It is further suggested that the pathways may be noradrenergic.