Cholinergic System in Behavior: The Search for Mechanisms of Action

. . . any theory of behavior is at present, and must be for some time to come, a theory. This is because neuroanatomy and physiology have not yet developed to a point such that they yield principles which may be employed as postulates in a system of behavior theory . . . (1). Some 40 years ago this statement by an internationally respected behavioral scientist recognized the importance of events intervening between changes in the environment, stimuli (S), and an organism'S (0) responses (R) to them. Relations between S � R are dependent upon intervening events and are influenced by them. R cannot be predicted solely on information about S; understanding the characteristics of 0 is essential, even when the simplest of Rs are involved. Although advances in concepts and technologies have enabled very significant strides in knowledge about the biochemical, electro­ physiological, and morphological properties of living organisms, there re­ main challenging questions about relations between the molecular events of these properties and the molar characteristics which constitute a fourth property of organisms, the behavioral property (2). The present review is concerned with examining speculative ideas and hypqtheses about .mechanisms of action by which the cholinergic neuro­ transmitter system may be involved in the behavior of living organisms as they cope with changes in their external and internal environments. Because most of the cholinergic receptors within the mammalian central nervous system (eNS) appear to be muscarinic (3), emphasis in this review will be