Effect of naloxone injected into the lateral cerebral ventricle on the arterial baroreflex sensitivity during heat stress-induced hyperthermia in rabbits

Abstract

The rabbits anaesthetized with urethane were made hyperthermic under heat stress. Effect of naloxone injected intracerebroventricularly on arterial baroreflex sensitivity (ABS) was investigated. The experimental animals were divided into two groups: the control and the naloxone-treated group. ABS decreased stepwisely in the control group when rectal temperature rose to over 40 °C. Mean arterial pressure (MAP) dropped markedly beyond 42°C. However, in the naloxone-treated group, ABS showed no significant change temperature reached 42°C. but it decreased dramatically at 43°C. Then, MAP was still maintained at about 90 mmHg. The results suggested that the marked reduction of ABS during hyperthermia might be related to endogenous opioid release.

Keywords

hyperthermia / arterial baroreflex sensitivity / naloxone / lateral cerebral ventricle injection

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