Expression of mRNA for the N-methyl-D-aspartate (NMDAR1) receptor and vasoactive intestinal polypeptide (VIP) co-exist in enteric neurons of the rat.

Anatomical, physiological and pharmacological evidence suggests that vasoactive intestinal polypeptide neurons are important mediators of the descending inhibitory component of intestinal peristalsis. Pharmacological data also indicate that glutamate may modulate intestinal motility. Recently, we demonstrated that mRNA coding for the glutamate N-methyl-D-aspartate (NMDA) receptor is expressed by rat enteric neurons. In order to ascertain whether NMDA receptor message is expressed by vasoactive intestinal polypeptide (VIP) neurons, we employed a double in situ hybridization technique. We hybridized tissue sections from the stomach, ileum and descending colon of adult rats with an NMDAR1 oligoprobe and a VIP oligonucleotide. Enteric neurons expressing mRNA for both NMDA and VIP were found in the myenteric and submucosal ganglia at all of the sampling sites. These data suggest that the mechanism for glutamatergic excitation is present in VIP-containing enteric neurons.