ABSTRACT
The integral role of pontine cholinergic nuclei in waking and thalamocortical activation is further emphasized by recent studies examining the behavioral state-related consequences of their inhibition, excitation or disinhibition. Hence, when pontine cholinergic neurons are directly inhibited, waking is significantly reduced. Ponto-geniculo-occipital (PGO) waves are field potentials that reflect synchronous activity of specific populations of central neurons. The appearance of PGO waves heralds the onset of rapid-eye-movement (REM) sleep and is believed to reflect cellular mechanisms that contribute to the initiation of this behavioral state. During REM sleep, the activity of the monoaminergic systems is negligible. Thus, the activation of the REM sleep state may be primarily, if not entirely, dependent on laterodorsal and pedunculopontine tegmental nuclei (LDT/PPT) cholinergic discharge. In addition, excitability is under the local control of adenosine, a neuromodulator with many characteristics indicative of its role in the LDT/PPT and basal forebrain as a sleep factor.
