2003 Volume 67 Issue 11 Pages 2501-2504
The effects of intracerebroventricular (i.c.v.) injection of bovine β-casomorphin-5 (β-CM-5: Tyr-Pro-Phe-Pro-Gly), a μ-opioid agonist derived from milk β-casein, on step-down type passive avoidance tasks were investigated in mice. Intracerebroventricular administration of a high dose (10 μg) of β-CM-5 produced a significant decrease in step-down latency. β-Funaltrexamine (5 μg, i.c.v.) almost completely reversed the β-CM-5-induced shortening of step-down latency, although neither naltrindole (5 ng, i.c.v.) nor nor-binaltorphimine (5 μg, i.c.v.) had any significant influence on the effect of β-CM-5. Meanwhile, a low dose (0.5 μg, i.c.v.) of β-CM-5 inhibited scopolamine (1 mg/kg)-induced impairment of passive avoidance response. These results indicated that a high dose of β-CM-5 induces amnesia, whereas a low dose ameliorates scopolamine-induced amnesia.
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