| Abstract: | Rat or hamster pups exposed to constant light or darkness since birth exhibit many circadian rhythms synchronized with those of the mother. During early development, a number of cues derived from the maternal circadian system synchronize the fetal and neonatal circadian clock. Maternal pineal sympathetic denervation during early pregnancy disrupts maternal synchronization of parotid α-amylase and testicular malate dehydrogenase circadian rhythms in rat pups. Maternal pineal sympathetic denervation was used to study potential agents able to synchronize the fetal or neonatal circadian clock. Melatonin injection to denervated pregnant mothers prevents the pineal sympathetic denervation effect on those circadian rhythms. We now studied the synchronizing effect of a benzodiazepine compound, diazepam. This GABAA agonist synchronized testicular malate dehydrogenase (MDH) activity of pups when it was injected to sympathetic denervated pregnant dams (a daily dose at 07:00 or 19:00 h from the 14 th to the 20 th day of gestation) or orally administered to the pups (a daily dose at 19:00 h from the 10 th to 24 th day of life). Co-injection of diazepam and GABAA antagonist, flumazenil, blocked the synchronizing effect of diazepam. The results demonstrate that diazepam has a synchronizing effect on the development of the circadian clock in rats and suggest that modulation of maternal GABAA could participate in mammalian maternal synchronization. |
