AN ANALYSIS OF THE EXCITATORY AND INHIBITORY EFFECTS OF SYMPATHETIC NERVE IMPULSES AND ADRENALINE ON VISCERAL SMOOTH MUSCLE

Abstract

The influence of adrenaline and sympathetic nerve impulses on various visceral muscles, particularly the uterus of the cat, was studied. During inhibition the excitability of these muscles is diminished or abolished, and conduction of muscular impulses is blocked. This effect may be considered as the direct cause of the diminution of motility during inhibition. However in the uterus adrenaline and sympathetic nerve impulses also have an excitatory action which is best demonstrated by the frequent occurrence of diphasic responses, in which inhibition is preceded by an increase in motility. Various observations, particularly the fact that adrenaline alone can give diphasic responses, make it improbable that this behavior is due to the presence of separate and specific excitatory and inhibitory nerve fibers. A theory is advanced which explains excitation and inhibition as 2 phases of the action of the same nerve impulses on smooth muscle.