Chemoreceptor responses to sympathetic stimulation and changes in blood pressure

Discharges from 24 single carotid chemoreceptor fibres were examined in 11 anaesthetized cats for the effects of mechanically induced alterations of arterial blood pressure and of stimulation of the preganglionic sympathetic nerve in the neck. In 10 fibres, discharge was increased when blood pressure was lowered: in the reamining 14 fibres, there was no apparent dependence of discharge upon blood pressure. Sixteen fibres increased their discharge in response to sympathetic stimulation, the remainder did not. Fibres were found which were: (a) sensitive to both blood pressure and sympathetic stimulation (6 fibres); (b) sensitive to neither (4 fibres), and (c) sensitive to one but not the other stimulus. The implications of these findings upon the hypothesis that local blood flow in the carotid body affects discharge in the steady state are discussed.