This study was undertaken to determine the effects of the destruction
of the medial preoptic area (mPOA) neurons by N-methyl D-aspartic acid
(NMDA), on sleep-wakefulness (S-W), locomotor activity, body weight,
rectal temperature, and food and water intake in rats. The NMDA lesion
of the mPOA produced long-lasting insomnia with marked reduction in t
he deeper stages of sleep, including paradoxical sleep. The reduction
in the duration of sleep episodes in the lesioned rats indicated their
inability to maintain sleep. The insomnia resulting from a decreased
sleep pressure did not alter the sleep-initiating ability. Though the
day-night distribution of sleep remained largely unaffected, there was
an increase in locomotor activity during the light period. There was
no increase in food intake to compensate for the high energy expenditu
re resulting not only from hyperactivity but also from hyperthermia in
the mPOA-lesioned rats. Thus, body weights of the rats were reduced e
ven without any change in food and water intake. However, the changes
in body temperature and locomotor activity after the mPOA neuronal los
s may not have exerted a major influence on S-W, as the alterations in
all these parameters had different time courses.