Proceedings of the Physiological Society

Abstract

It is commonly held that the stimulation of the carotid sinus nerve produces a fall in blood pressure. In a number of experiments, however, stimulation of the carotid sinus nerve in cats has given the opposite result.Cats were anaesthetized by intravenous injection of chloralose (0*08-01 g./kg. body weight). The carotid sinus nerve was exposed and stimulated using a square wave electronic stimulator. This device allowed independent Chloralose anaesthesia.variation of frequency of stimuli (1.5-100 cyc./sec.), pulse duration (0-02-1.0 m.sec.) and voltage output (1-2 V.). Stimulation of the carotid sinus nerve (containing afferents from the carotid sinus and carotid body) markedly raises the arterial blood pressure. The pulse duration of the stimulus chiefly determines the degree of pressor response. Thus the threshold duration at a frequency of 100 cyc./sec. and 2 V. is 0-02 m.sec. Maximal effects (pressure increases of 60-100 mm. Hg) are mainly observed using -stimuli of 0-1 m.sec. duration (Fig. 1).The pressor effects persist after double vagotomy, destruction of the contralateral carotid sinus nerve, excision of the cervical sympathetic, section of the glossopharyngeal nerve peripheral to the junction of the carotid sinus