Role of vagal afferent C fibres in the bradycardiac response to an increase in arterial blood pressure in ferrets

Abstract

The effects on baroreceptor reflexes of bilateral application of the C fibre neurotoxin, capsaicin, to the cervical vagi have been investigated in decerebrate ferrets. Baroreflex sensitivity was estimated from the relationship between cardiac interval and systolic blood pressure following I.V. infusion of phenylephrine. Control responses to phenylephrine were fitted by two linear slopes with an initial shallow slope, a, followed by a steeper slope, b. Capsaicin abolished slope b and the resulting relationship was best fitted by a single regression with a slope not significantly different from that of the control response a. This suggests that a significant proportion of the baroreflex response induced by phenylephrine is mediated by cardiopulmonary receptors attached to vagal afferent C fibres.