RESPONSES OF LARYNGEAL CAPSAICIN-SENSITIVE RECEPTORS TO VOLATILE ANESTHETICS IN ANESTHETIZED DOGS

The responses of laryngeal capsaicin (CAPS)-sensitive receptors to hal othane, enflurane, isoflurane and sevoflurane were evaluated in anesth etized spontaneously breathing dogs from the afferent activity of the internal branch of the superior laryngeal nerve. The CAPS-sensitive re ceptors were clearly distinguished from irritant receptors by their re sponsiveness to CAPS and their lack of responsiveness to water. All th e CAPS-sensitive receptors were significantly stimulated by all volati le anesthetics in a concentration-related manner, and the activation b y halothane, enflurane, and isoflurane was significantly greater than by sevoflurane. In contrast, responses of irritant receptors to the vo latile anesthetics were divided into three types (stimulation, inhibit ion or non-response), and did not differ among anesthetics. In conclus ion, the present study demonstrated that the CAPS-sensitive receptors were consistently stimulated by halogenated volatile anesthetics and e specially by halothane, enflurane, and isoflurane, and that these resp onses were dissimilar to the variable responses of irritant receptors. (C) 1998 Elsevier Science B.V. All rights reserved.