Changes in sleep–wakefulness after 6-hydroxydopamine lesion of the preoptic area

Abstract This study was undertaken to assess the role of catecholamine fibers, terminating in the preoptic area, in regulating sleep–wakefulness in rats. Sleep–wakefulness was assessed on the basis of 24 h electroencephalogram, electromyogram and electro-oculogram recordings before and after destruction of catecholaminergic terminals at the medial preoptic area by bilateral intracerebral injection of 6-hydroxydopamine (8 μg in 0.2 μl). There was a mild reduction in sleep and increase in wakefulness after the lesion. The increase in active wakefulness observed after eight days of lesion persisted even on the 12th day. In spite of the reduction in sleep, the day–night sleep ratio was not affected by 6-hydroxydopamine lesion of the preoptic area. The results indicate that the noradrenergic fibers at the preoptic area have a hypnogenic role.