Efeito anestésico geral do mentol: avaliação da inibição de reflexos autonômicos cardiovasculares

Abstract

The present study aimed to analyze the possible anesthetic effect of menthol in Wistar rats focusing on the inhibition of cardiovascular autonomic reflexes. Thus, after the administration of doses that induced immobilization, the following parameters were analyzed while a pressure stimuli was applied to the hind paw of these animals: (I) mean arterial pressure and heart rate alterations (measured via cannulation of the femoral artery and magnification of the mechanoelectric signal using a pressure transducer); (II) time for loss of straightening reflexes and presence of paw withdrawal reflex; (III) hypnosis time. The administration of ketamine plus xylazine in subanesthetic doses was used as positive control. Both the hypnosis time and the latency for hypnosis induction were greater in animals treated with menthol when compared with controls. Neither the number of animals that lost the straightening reflex nor the number of animals that presented paw withdrawal reflex were different related to controls. Despite the loss of withdrawal reflex, animals treated with menthol still presented cardiovascular alterations in response to the pressure stimuli on the paw; a similar result was observed after the administration of ketamine plus xylazine. Therefore, the hypnotic and antinociceptive effects of menthol are not enough to produce surgical anesthesia.