| Abstract: | In a recent study, we observed circadian rhythms in the response to subcutaneous (s.c.) administration of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), a serotonin (5-HT)1A receptor agonist, in rats. Although these results suggested a circadian rhythm in the function of the central 5-HT1A receptor, it was not possible to completely exclude drug disposition as the generating factor. The present study investigated circadian rhythms in the behavioral responses to intracerebroventricular administration of 8-OH-DPAT in rats. The results indicated the existence of circadian rhythms of a similar pattern to those observed in the forepaw treading and head weaving responses to s.c. administration of the drug. The flat body posture response observed following s.c. drug administration was not evident in the present study. These observations suggest that the central postsynaptic 5-HT1A receptor exhibits a circadian rhythm in its function. |
