Effects of a new TRH analogue, YM-14673 on the central nervous system

The effects of a new TRH analogue, YM-14673 (N alpha-[[S)-4-oxo-2-azetidinyl)carbonyl]-L-histidyl-L-prolinamide dihydrate) on the central nervous system were compared with those of TRH. YM-14673 was 10-40 times more potent than TRH in antagonizing pentobarbital-induced sleep and hypothermia, and ethanol-induced hypothermia in mice. YM-14673 accelerated recovery from disturbed consciousness induced by concussive head trauma in mice and normalized the behavior and spontaneous EEG disturbed by electrolytic lesion of the hypothalamus in cats with 25-100 times greater potency than that of TRH. In the tests on pentobarbital sleeping time and EEG disturbance, the cerebral activating activity of YM-14673 was 8-36 times longer-lasting than that of TRH. These results indicate that YM-14673 possesses potent arousal effects on the central nervous system. The mode of action of YM-14673 was also discussed.