THE RÔLE OF THE INFERIOR MESENTERIC GANGLIA IN THE DIPHASIC RESPONSE OF THE COLON TO SYMPATHETIC STIMULI

Abstract

In barbitalized dogs small intraven. doses of adrenalin, and faradic stimulation of the peripheral stump of either the lumbar colonic nerve or the presacral (hypogastric) nerves produced primary inhibition, followed by a marked increase in tone and contractions in all segments of the colon. After presacral stimulation, the 2 phases were obtained constantly only in the distal segments. The height of the motor phase, and the duration of the inhibitory phase in all segments were altered by division of the spinal rami of the inferior mesenteric ganglia, the motor phase being usually increased in height, and the inhibitory phase prolonged in the lower segments. After constant responses to any of the stimuli had been established following division of the rami, section of either the lumbar colonic or the presacral nerves produced further modification: a reduction in the height of the motor phase, and an increase in the duration of the inhibitory phase. After section of the presacrals alone the increase in the inhibitory phase was most marked in the distal segment; after section of the lumbar colonies alone, in both the proximal and the distal segment. If the presacrals were divided, subsequent section of the lumbar colonies sometimes decreased the duration of the distal inhibitory phase. The response of the internal sphincter of the anus to all these types of stimuli is usually triphasic: a primary motor phase coinciding with colonic inhibition, an interval, and a 2d motor phase at the time of the motor phase in the distal colon segment. Section of the rami or of either postganglionic trunk reduces the height of the 1st motor phase. The interval undergoes the same change as the distal inhibitory phase. The height of the motor phase is increased in all segments, including the sphincter, if adrenalin is injected during the motor phase of a preceding postganglionic faradization, and the inhibitory phase is usually shortened. After a lumbar colonic stimulation the adrenalin inhibition is decreased in all segments; after a presacral stimulation the adrenalin inhibition is decreased in the distal segment. The ganglion cells of the inferior mesenteric ganglia are shown by these data to be active independently of preganglionic influences, and to exert, through efferent fibers in the postganglionic stretch, influences upon which the peripheral effect of these stimuli depends. Since the demonstrated influence of the centrally isolated postganglionic trunks consists in maintenance of time and intensity relationships between one segment of the colon and another during the response, it is tentatively concluded that intersegmental relationships play a part in the response of any segment to these stimuli, and that the value of the postulated intersegmental influences depends on either an automatic or a reflex activity of the cells of the inferior mesenteric ganglia.