ACTIVITY FOLLOWING COLONIC DISTENSION IN ENTERIC SENSORY FIBERS PROJECTING TO THE INFERIOR MESENTERIC GANGLION IN THE GUINEA-PIG

In this investigation the characteristics of the response to colonic d istension of afferent fibres projecting to the inferior mesenteric gan glion (IMG) of the guinea pig were studied in vitro. Intracellular mem brane potential recordings were made from neurons in the IMG. Post-syn aptic potentials arising from activity in afferent fibres were recorde d in these cells following distensions of a small segment of colon pla ced in a separate and independently perfused organ bath. These afferen t fibres showed both transient and sustained responses to distension. Application of a solution containing 0.25 mM Ca2+ and 10 mM(2+) Mg2+ t o the colon (but not to the IMG) reduced the overall response but did not abolish the activity in these fibres. It is concluded that some af ferent fibres which respond to colonic distension project directly to the IMG.