Discharge patterns of neurons in cholinergic regions of the basal forebrain during waking and sleep

A subset of neurons recorded in the magnocellular basal forebrain (mBF) of cats and rats exhibit elevated discharge rates during waking and REM sleep, and diminished discharge during sleep with cortical EEG synchrony (nonREM sleep). This pattern is observed in mBF neurons in cats with identified asc ending projections, and in neurons located in cholinergic regions of the ra t mBF. However, the cholinergic versus noncholinergic nature of recorded ce lls could not be determined with the extracellular recording method employe d. During waking, discharge of mBF neurons is strongly movement-related. Pe ak discharge rates occur during a variety of head and limb movements. Disch arge rates during waking immobility are reduced by >50% compared to rates d uring waking movement. The absence of movement accounts for more of the var iance in discharge across the sleep-wake cycle than does the presence of co rtical EEG synchronization. Several factors participate in the regulation o f mBF neuronal activity across arousal states. Tonic inhibition mediated by adenosine appears to be present during both waking and sleep. In some mBF neurons, increased GABAergic inhibition contributes to nonREM sleep-related reductions in discharge rate. Fluctuations in mBF cell activity during wak ing behaviors may reflect changing excitatory input from neurons in the pon tine and midbrain tegmentum. (C) 2000 Elsevier Science B.V. All rights rese rved.