Naltrexone Protects Against Hypotension, Hyperthermia, and β-Endorphin Overproduction During Heatstroke in the Rat

[摘要] References(33)Cited-By(5)Heat stroke is characterized by hyperthermia, arterial hypotension, decreased baroreflex sensitivity, and increased serum levels of β-endorphin. Whereas naltrexone may have therapeutic potential in heat stroke, the underlying mechanism remains unclear. We tested the hypothesis that naltrexone may attenuate heat stroke by reducing hyperthermia, hypotension, decreased baroreceptor sensitivity, and/or increased serum levels of β-endorphin. Heat stroke was induced by exposing the anesthetized adult Sprague-Dawley rats in an incubator at 43°C. The moment in which the mean arterial pressure dropped irreversibly from the peak level was taken as the onset of heat stroke. Control rats were exposed to 24°C. Mean arterial pressure, baroreceptor sensitivity, and maximal reflex bradycardia, after the onset of heat stroke, were all significantly lower than in control rats. However, rectal temperature and serum levels of β-endorphin were all greater after the onset of heat stroke. Intravenous delivery of naltrexone (10 mg/kg) 20 min before the initiation of heat stress, but not immediately at the onset of heat stroke, significantly attenuated the above-mentioned reactions. Accordingly, naltrexone improved survival during heat stroke. These results suggest that naltrexone protects against hypotension and decrement of both baroreceptor sensitivity and maximal reflex bradycardia during heat stroke by reducing both hyperthermia and increment of serum β-endorphin and thus improves survival.

[学科分类] 药学

[关键词] blood pressure;heatstroke;β-endorphin;naltrexone