Is there an interaction between catecholamines and enkephalins in the inferior mesenteric ganglion of the cat?

The authors attempted to block the effects of enkephalins in the lower mesenteric ganglion of the cat by injection of Nalorphin--the antagonist to morphine. In the ganglion they observed an accumulation of catecholamines in nerve cells, nerve terminals and SIF cells. The inhibitory action of enkephalins to catecholamines secretion from nerve cells was assumed.