EFFECTS OF BRAIN NATRIURETIC PEPTIDE ON EFFECTS OF MORPHINE IN MICE

Brain natriuretic peptide (BNP) is a member oi the natriuretic peptide family. The effects of intracerebroventricularly administered BNP (in 0.002-200 ng doses) on the analgesic, tolerance-inducing and dependen ce-inducing actions of morphine were investigated in adult male CFLP m ice. Graded doses of BNP centrally did not affect pain sensitivity its elf in a fail-flick test. However, different doses ai BNP depressed th e acute nociceptive effect of a single subcutaneous dose of morphine ( 5 mg/kg), and BNP attenuated the development of acute and chronic tole rance to morphine. Withdrawal signs were studied by injecting naloxone (1 mg/kg s.c.), There was no significant difference in symptoms betwe en the tolerant group and animals treated with BNP. The data obtained indicate that BNP can modify the analgesic action of morphine.