Effects of triazolam and nifedipine injections into the medial preoptic area on sleep.

We have reported previously that microinjections of the benzodiazepine (BZ) hypnotic triazolam into the medial preoptic area (MPA) of the hypothalamus increase sleep in the rat. As a follow up to previous work, which has indicated that the dihydropyridine calcium channel blocker, nifedipine, prevents sleep induction by an intraperitoneally administered BZ, we have now coinjected nifedipine and triazolam into the MPA. It was found that nifedipine alone had no significant effects on sleep and prevented sleep induction by triazolam. There were no drug-specific effects on core temperature in any treatment condition. These data suggest that dihydropyridine-sensitive sites may be involved in the mechanism of sleep induction by BZs.