Ventrolateral preoptic nucleus

The ventrolateral preoptic nucleus (VLPO), also known as the intermediate nucleus of the preoptic area (IPA), is a small cluster of neurons situated in the anterior hypothalamus, sitting just above and to the side of the optic chiasm in the brain of humans and other animals. The VLPO, together with the reticular activating system and the widely projecting orexin neuronal system that originates in the lateral hypothalamus, are the interconnected neural systems which control states of arousal, sleep, and transitions between these two states. The VLPO is active during sleep, primarily during non-rapid eye movement sleep (NREM sleep), and releases inhibitory neurotransmitters, mainly GABA and galanin, which inhibit neurons of the reticular activating system that are involved in wakefulness and arousal. The VLPO is in turn innervated by neurons from the aforementioned neural systems. The VLPO is activated by the sleep-inducing neurotransmitters serotonin and adenosine. and endosomnogens; Prostaglandin D2 The VLPO is inhibited during wakefulness by the arousal-inducing neurotransmitters norepinephrine and acetylcholine. The role of the VLPO in sleep and wakefulness, and its association with sleep disorders - particularly insomnia and narcolepsy - is a growing area of neuroscience research.