Adrenalectomy abolishes and cortisol restores naloxone's beneficial effects on cardiovascular function and survival in canine hemorrhagic shock.

Endogenous opioid substances are activated in and may contribute to the cardiovascular depression of hemorrhagic shock. In order to determine the importance of the adrenal gland in the beneficial effects of the opiate antagonist naloxone in shock we studied 23 adrenalectomized dogs subjected to hemorrhagic shock. Adrenalectomy abolished the salubrious cardiovascular responses to naloxone. Naloxone responses (increased mean arterial pressure, cardiac output, and left ventricular contractility) were restored by giving hydrocortisone 50 mg intravenously before naloxone. Survival was also prolonged in animals receiving naloxone and hydrocortisone compared to naloxone or saline alone; hydrocortisone alone decreased survival. The adrenal glands are necessary for naloxone's beneficial effects, probably via adrenal corticosteroid secretion.