EFFECT OF NALOXONE ON CEREBELLAR CGMP CONTENT - POSSIBLE GABA-ANTAGONISTIC ACTION

Naloxone in high doses (60-240 mg/kg, i.p.) produced a dose-dependent increase in cerebellar c[cyclic]GMP content of mice. The rise in cGMP content reached its maximum within 5 min and was of short duration. Short-lasting episodes of clonic seizures were noted after 240 mg/kg naloxone. Low doses of naloxone (5-10 mg/kg) had no effect on cerebellar cGMP content but markedly potentiated the increase in cGMP induced by isoniazid. Naloxone (5 mg/kg) partially antagonized the fall in cGMP elicited by diazepam but had only a slight effect on the action of pentobarbital (30 mg/kg, i.p.). Naloxone may exert GABA antagonistic effects aside from the potent opiate receptor antagonistic activity.