Antianaphylactic effect of naloxone in mice is mediated by increased central sympathetic outflow to sympathetic nerve endings and adrenal medulla.

Intravenous naloxone, 1 or 10 mg/kg, protects sensitized mice from lethal anaphylaxis. The protective effect is reversed by pretreatment with the ganglionic blocker, chlorisondamine chloride, peripheral chemical sympathectomy with 6-hydroxydopamine or bilateral adrenal gland denervation. The possible involvement of the sympathetic nervous system in naloxone's antianaphylactic action, suggested by these findings, is discussed.