ACTIVATION OF VENTROLATERAL PREOPTIC NEURONS DURING SLEEP

The rostral hypothalamus and adjacent basal forebrain participate in t he generation of sleep, but the neuronal circuitry involved in this pr ocess remains poorly characterized. Immunocytochemistry was used to id entify the FOS protein, an immediate-early gene product, in a group of ventrolateral preoptic neurons that is specifically activated during deep. The retrograde tracer cholera toxin B, in combination with FOS i mmunocytochemistry, was used to show that sleep-activated ventrolatera l preoptic neurons innervate the tuberomammillary nucleus, a posterior hypothalamic cell group thought to participate in the modulation of a rousal. This monosynaptic pathway in the hypothalamus may play a key r ole in determining sleep-wake states.