Inhibition of intestinal secretion without reduction of cyclic AMP levels.

Net water transport by the jejunum of anaesthetized rats was measured together with jejunal cyclic AMP content. Vasoactive intestinal peptide stimulated secretion and elevated the cyclic AMP level. Morphine (10 mg/kg s.c.) inhibited the stimulated secretion but failed to depress the cyclic AMP accumulation. It is suggested that cyclic AMP may not be the mediator of intestinal fluid secretion. Alternatively, morphine may block the secretory effect of cyclic AMP elevated by vasoactive intestinal peptide.