PHARMACOLOGICAL CHARACTERIZATION AND DIFFERENTIATION OF NONCHOLINERGIC NUCLEUS BASALIS NEURONS IN-VITRO

USING intracellular recordings in guinea pig brain slices, the pharmac ology of electrophysiologically identified and immunohistochemically c onfirmed non-cholinergic nucleus basalis neurons was studied to determ ine their response to the major neurotransmitters of the subcortical a fferents to this region. The cells were differentiated into three type s: Type A cells (similar to 44%) were depolarized by noradrenaline (NA ) and muscarine, Type B cells (similar to 23%) were depolarized by NA but hyperpolarized by muscarine, and Type C cells (similar to 15%) wer e hyperpolarized by both agonists. These cell types were also differen tially responsive to serotonin (hyperpolarizing B, C) and histamine (d epolarizing A, B). Accordingly, the non-cholinergic neurons share cert ain discharge properties but appear nonetheless to comprise distinct t ypes which respond differentially to the major modulatory neurotransmi tters and thus play potentially different roles in cortical modulation across the sleep-wake cycle.