The ascending mesolimbic cholinergic system--a specific division of the reticular activating system involved in the initiation of negative emotional states.

The review summarizes evidences from extensive studies suggesting that ascending mesolimbic cholinergic system (AMCS) that terminates in vast areas of forebrain and diencephalic limbic areas is responsible for specific generation of aversive arousal and aversive emotional state. This state is accompanied by emission of threatening and/or alarming vocalizations that served as a quantitative measure of the emotional response. The AMCS originates from the cholinergic neurons within the laterodorsal tegmental nucleus that have widespread and diffuse ascending connections. Activity of the AMCS induced by activation of the muscarinic cholinergic receptors in the terminal fields of this system, or by glutamate stimulation of neurons of the laterodorsal tegmental nucleus, brings about aversive state with alarming vocalizations. It is postulated that release of acetylcholine from the terminals of the AMCS in the vast areas of the forebrain and diencephalon serves as the initiator of the aversive emotional state with concomitant manifestations and alarming vocal signaling. It is concluded that the AMCS serves as a specific physiological, psychological, and social arousing and alarming system.