[Hypogenic cholinergic neuronal route in the central nervous system]

Because of the extensive overlapping within the brain of arousing and hypnogenic neurons the method of electrical stimulation has proved unsuitable for mapping out specific hypnogenic structures. On the other hand, the method of localized chemical stimulation achieved by introducing minute crystals of chemical substances permits the dissection of adjacent neurons with different functions. The aim of this study was to map out the central hypnogenic pathways introducing minute crystals of acetylcholine, eserine or atropine in different brain regions through cannulae permanently implanted in the brains of cats. The behavioral effects produced by the chemical stimulus were monitored simultaneously with electrical recordings from the neocortex, olfactory bulb, enthorinal cortex, and eyes movements. It is concluded that there is a sleep system made up of a multisynaptic chain of short axon neurons with cholinergic synaptic transmission and which extends throughout all the levels of the neuroaxis.