[Regulation of dopamine neurons in ventral tegmental area on sleep-wakefulness]

The effects of microinjection of gamma-aminobutyric acid (GABA) and serotonin (5-HT) into the ventral tegmental area (VTA) on the activity of dopamine neurons in VTA and sleep-wakefulness were studied in rats. It was observed that in aneasthetized rats microinjection of GABA (25 micrograms) and 5-HT (2 micrograms) respectively decreased or increased the level of 3, 4-dihydroxyphenylacetic acid (DOPAC) to 68.2% (P < 0.01) and to 136.1% (P < 0.01) of control value in the nucleus accumbens (Acb). It was also observed that in free moving rats the time of wakefulness was respectively decreased and increased by the two drugs. Furthermore, the time of wakefulness was enhanced following microinjection of dopamine (10 micrograms) into Acb, an effect that could be blocked by haloperidal (16 pmol), but not by SCH23390 (2 nmol). The above results suggest that bilateral microinjection of GABA and 5-HT into VTA could exert respectively an inhibitory or an excitatory action on the dopamine neurons in VTA, mediating the sleep-wakefulness effect probably through the mesolimbic system.