Time-dependent variations in aversively motivated behaviors: Nonassociative effects of cholinergic and catecholaminergic activity.

Abstract

The role of acetylcholine and central catecholamines in modulating aversively motivated behaviors, and behavior following exposure to uncontrollable stressors, is evaluated. In the presence of adequate associative processes, nonassociative factors, mediated by stress-induced neurochemical changes, may determine avoidance response rate. In addition to the existence of a balanced-state between excitatory catecholamine and inhibitory cholinergic systems, these neurochemical systems may be mutually regulatory. Excessive stimulation of 1 system may induce a compensatory antagonistic rebound in the complementary system, thereby maintaining neurochemical homeostatis. Owing to time-dependent variations in neurotransmitter activity, temporal variations in the animal''s performance may occur following initial exposure to aversive stimulation. Alterations in neurochemical activity that affect nonassociative processes have predictable effects on time-dependent variations in avoidance performance. The model is extended to deal with other stress related phenomena, e.g., helplessness, depression and ulceration.