CAPSAICIN INHIBITS RESPONSES OF FINE AFFERENTS FROM THE KNEE-JOINT OF THE CAT TO MECHANICAL AND CHEMICAL STIMULI

In adult anaesthetized cats we studied the effects of capsaicin on the responses of single slowly conducting afferents of the knee joint to mechanical and chemical stimuli (bradykinin). An intra-arterial bolus injection of capsaicin into the joint reduced or abolished the responses to passive movements of the joint in 8 of 19 afferents and the responses to intra-arterially administered bradykinin in 10 of 11 units. Capsaicin was usually effective at 10-4 to 10-3 M. The inhibition was predominantly observed in nociceptive afferents, whereas most low threshold units were not desensitized. © 1990.