Opiate antagonists reverse the hypoactivity associated with systemic anaphylaxis in mice.

Systemic anaphylaxis in the mouse is associated with marked hypoactivity. This effect is reversed by treatment with the opiate antagonists, naloxone (5-10 mg/kg) or naltrexone (1 mg/kg). Administration of naltrexone methyl bromide (1 mg/kg), a selective peripherally acting opiate antagonist, is ineffective in reversing the hypoactivity induced by anaphylaxis. These results suggest a role for central nervous system opiate mechanisms in the hypoactivity induced by anaphylaxis. They support the hypothesis that endogenous opiates contribute to the pathophysiologic consequences of anaphylactic shock.