Cholinergic neurotransmission, REM sleep and depression.

It is known from animal experiments that the regulation of REM and Non-REM sleep is governed by cholinergic and serotonergic/adrenergic neurons in the brain stem. Cholinergic neurons in the gigantocellular field of the tegmentum seem to be responsible for the triggering and maintenance of REM sleep. These findings are of special interest for interpreting abnormalities of REM sleep in depression. Psychiatric sleep research in the last two decades has demonstrated that an early onset of REM sleep and heightened REM density frequently occurs in patients suffering from depression. Extrapolating from animal data on REM sleep regulation, the premature onset of REM sleep in depression may be interpreted as the consequence of a central nervous cholinergic overactivity or muscarinic supersensitivity. In our experimental work we have tested assumptions of the so-called reciprocal interaction model of NonREM and REM sleep by cholinergic/anticholinergic stimulation strategies of sleep in healthy subjects. Furthermore, the impact of cholinergic stimulation on sleep in depression, healthy control subjects and other psychopathological conditions was investigated. These studies demonstrated that the most pronounced REM sleep response to cholinergic stimulation occurred in depression.