CHOLINERGIC

Activated or transmitted by acetylcholine. Acetylcholine is one of the two types of “chemical transmitters” in the nervous system; the other type includes adrenalin and nor- adrenalin.Recent investigations indicate that messages in the nervous system are transmitted electrically in the body of the nerve fiber, but chemically at the synapse or junction between fibers (see Fig. 40). The chemical, acetylcholine, is synthesized and stored in the terminals of the axon fibers and released by spike potentials, or nerve impulses (Von Euler, 1959, and De Robertis et al., 1963). Cholinergic transmission occurs primarily at the synapses of motor fibers and striped muscles, at synapses in the parasympathetic portion of the autonomic nervous system (controlling the smooth muscles), and in the central nervous system as well—for example, in the neural mechanisms for thirst (Grossman, 1960; Fisher and Coury, 1962).In view of the stimulating effects of acetylcholine on the brain and nervous system, a number of cholinergic drugs have been developed. These drugs are classified as activators or antidepressants, and one of them, Deaner, has been applied with some success to schizophrenic patients (Berger, 1960). In addition, acetylcholine has been employed in attempts to measure autonomic changes accompanying emotional disturbances. In the Funkenstein test (1952), originally developed to predict the outcome of electroshock treatment, Mecholyl (acetylcholine) is injected intramuscularly and its effect on blood pressure observed for several minutes. Some psychiatrists find that a drop in blood pressure indicates that the patient will benefit from electroshock treatments or from psychotherapy. There are also indications that this response occurs only when the subject is in an emotional state of fear or anxiety, and for this reason the test is sometimes used as a diagnostic indicator of neurotic reactions to stress.