Preoptic area sleep-active neuron

Morairty, S., Rainnie, D., McCarley, R. Greene, R. (2004). Disinhibition of ventrolateral preoptic area sleep-active neurons by adenosine a new mechanism for sleep promotion. Neuroscience 123 (2), 451-7. 

Figure 2.4 Flip-flop switch model of wake and slow wave sleep active systems. Mutually inhibitory connections exist between GABAergic/Galaninergic slow wave sleep active neurons in the ventrolateral preoptic area (VLPO) of the anterior hypothalamus and aminergic neurons in the hypothalamus (histamine (HA) neurons in the tuberomammillary nucleus (TMN)) and brainstem (serotonin (5-HT) neurons in the dorsal raphe (DR) and noradrenaline (NA) neurons in the locus coeruleus (LC)). Orexinergic neurons in the perifornical hypothalamus (PFH) stabilize the waking state via excitation of the waking side of the flip-flop switch (aminergic neurons).

Sleep-active neurons have been identified in the ventrolateral and medial preoptic areas. These neurons exhibit increased discharge during SWS and REMS rather than W. Sleep-active neurons colocalize GABA and are excited by adenosine and prostaglandin D2 (McGinty Szymusiak, 2001) (Table 9.3). 

An unanswered question about adenosine is how this inhibitory neurotransmitter activates the ventrolateral preoptic area of the hypothalamus (VLPO), which contains a population of sleep-active neurons and is hypothesized to be... 

Immunohistochemical and electrophysiological studies of the hypothalamic preoptic area (POA), which plays a major role in sleep promotion, have identified a subset of sleep-active ventrolateral POA (VLPO) neurons (Sherin et al. 1996 Szymusiak et al. 1998). A tightly clustered group of VLPO neurons appears to promote non-REM sleep, by suppression of the histaminergic arousal system, which... 

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