The actions of prostaglandins E2, A2 and F22 on the sensory receptors of the carotid bifurcation have been investigated. Electrical activity of baroreceptor and chemoreceptor fibres was recorded from the sinus nerve of anaesthetized cats. Prostaglandins elicited alterations in blood pressure which were accompanied by changes in baroreceptor activity. Chemoreceptor spontaneous activity was modified by the injection of prostaglandins; such variation did not occur in vitro and thus appears to be secondary to changes in carotid blood flow. We have been unable to demonstrate any action of the prostaglandins at the concentrations studied on baroreceptors or chemoreceptors of the carotid bifurcation, apart from changes secondary to vascular effects.There are reports based on indirect evidence which suggest that prostaglandins can affect sensory receptors in the carotid artery. For example, Carlson and Oro [1966] have proposed that prostaglandin E1 (PGE1) may have 'direct actions on the carotid artery or on structures in this artery' to evoke reflex vascular changes in dogs. Kaplan, Grega, Sherman and Buckley [1969] have reported that in dogs part of the hypotensive response to PGE1 administration results from actions on the carotid sinus-body structures, most likely the baroreceptors. However, McQueen [1972] examined the respiratory and vascular responses of the cat to various prostaglandins and concluded that it is unlikely that either the carotid baroreceptors or chemoreceptors are directly involved in the responses, but without electrophysiological evidence could not preclude the possibility.The object of this study was to establish directly whether prostaglandins affect sensory discharges recorded from baroreceptor and chemoreceptor units in the carotid sinus nerve of the cat. The results indicate that the observed changes in baroreceptor and chemoreceptor activity are secondary to vascular changes, and that prostaglandins in the concentrations studied do not affect directly the sensory receptors of the carotid bifurcation.
METHODSCats of either sex (2-0-2-7 kg) were anaesthetized with sodium pentobarbital (Diabutal, 40 mg/kg i.p.). A femoral vein was cannulated and used for drug administration, the catheter tip lying in the mid-abdominal region. A cannula was inserted into the