Regulation of posterior lateral hypothalamic arousal related neuronal discharge by preoptic anterior hypothalamic warming.

The posterior lateral hypothalamus (PLH) is a brain region involved in cortical activation and maintenance of behavioral arousal. Spontaneous and evoked neuronal activities were recorded in the PLH of cats before and during local warming of the preoptic-anterior hypothalamus (POAH). Forty-six percent of PLH neurons recorded in awake cats decreased spontaneous discharge during POAH warming. In the absence of POAH warming, these same cells exhibited significantly lower discharge rates in non-rapid eye movement (NREM) sleep compared to waking. Responses of PLH neurons to POAH warming were also investigated in sleeping cats to determine whether hypothalamic thermosensitive neurons modulated sleep-wake regulation across arousal states. POAH warming had no influence on spontaneous activities of PLH neurons during NREM sleep, but suppressed activity of a small subset of neurons during rapid eye movement (REM) sleep. Thus, during wakefulness or REM sleep, hypothalamic thermosensitive neurons may modulate behavioral state via inhibition or disfacilitation of arousal systems.