|Budget Amount *help
¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1990 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1989 : ¥1,300,000 (Direct Cost : ¥1,300,000)
To elucidate the physiological role of opioid peptides as the regulator of brain function, with special reference to learning and memory process, the effect of morphine on the process was investigated using one-trial step-down and/or step-through type passive avoidance learning test in mice. Following findings were obtained.
1. Pre-training administration of morphine impaired acquisition of memory, on the contrary, pre-test morphine facilitated memory retrieval.
2. Amnesia induced by scopolamine, cycloheximide and electroconvulsive shock was also reversed by pre-test morphine. These results may suggest that the effect of morphine is due to its direct action on the process but not to the state dependent effect.
3. Both effects of morphine, inhibition of memory acquisition and facilitation of memory retrieval, are antagonized by naloxone, a selective mu-opioid receptor antagonist. The participation of mu-receptors in the process was supported by the following results ; a) pre-test administration of DTLET, a selective delta-opioid receptor agonist, did not produce the same effect as morphine. b) nor-binaltorphimine, a selective kappa-receptor antagonist, did not antagonize the effect of pre-test morphine.
4. The facilitation of memory retrieval by pre-test morphine was also demonstrated in the amnesic animals produced by hypoxia, cerebral ischemia, and intracerebroventricular injection of anti-arginine vasopressin anti-serum.