雄ラットのジアゼパム誘導性再認記憶障害における精巣の関与についての検討

抄録

Benzodiazepines, including diazepam (DZP), induce recognition memory impairment as a side effect, and in this class of drug, there are sex differences in pharmacokinetics and pharmacodynamics. Therefore, we focus on whether the effect of DZP on recognition memory depends on sex difference. Our previous study showed the improvement effects of ovaries on recognition memory deficit induced by DZP in female rats. Here we examined the influence of testes on DZP-induced recognition memory impairment in male rats. Recognition memory was assessed by a spontaneous object recognition (SOR) and a spontaneous place recognition (SPR) tests that utilize the natural tendency of rats to explore a novel stimulus more than the familiar one. Thus, if rats could retain the object identity or place information, they explored a novel object or place more than the familiar one. First, using intact male rats, we examined the effect of DZP on SOR and SPR tests. Rats treated with DZP (2.0 mg/kg, i.p.) or vehicle, explored a novel object more than the familiar one in the SOR test, but in the SPR test, they with DZP, but not vehicle, investigated equally two objects. Second, we had castrated intact male rats, and then, the SOR and SPR tests were conducted. Results showed that in the SOR test, they with DZP or vehicle explored a new object more than the familiar one, but in the SPR test, they with DZP, but not vehicle, explored equally two objects. These results suggest that male rats even with DZP could retain the object identity, but not place information, regardless of whether or not castration was conducted.