Role of aortic chemoreceptors in the hypertensive response to cigarette smoke

To determine the role of aortic chemoreceptors in the rise of systemic blood pressure (BP) seen with smoking cigarettes, their responses to injecting various doses of nicotine (Nic) into the left atrium and to a puff of cigarette smoke were studied in 31 cats. The activity of 71% (n = 36) of the chemoreceptor fibres was stimulated significantly by a puff of cigarette smoke (delivering approximately 10.0 micrograms kg-1 Nic). The mean threshold dose to stimulation by nicotine of these fibres was 8.0 micrograms kg-1. The activity of the remaining 29% (n = 15) was not stimulated; their mean threshold dose to stimulation by Nic was 24 micrograms kg-1. Stimulation of fibres lasted for about 14 +/- 0.2 sec and the rise in BP was seen for 20-60 sec. By using hexamethonium it was established that the stimulation was produced exclusively by Nic contained in cigarette smoke. It was concluded that aortic chemoreceptors must contribute to the reflex rise in BP produced by smoking cigarettes.