N-Methyl-d-aspartic acid (
NMDA) receptors are known to function in the mediation of
pain and have a significant role in the development of
hyperalgesia following
inflammation.
Serine phosphorylation regulation of
NMDA receptor function occurs in a variety of conditions. No studies have demonstrated a change in phosphorylation of enteric
NMDA receptors following colonic
inflammation. We examined the levels of
NMDA NR1 phosphorylation in trinitrobenzene
sulfonic acid (TNBS) induced
colitis in rats and compared it to protein translation and the development of visceral
hypersensitivity. We have previously, demonstrated an increase in the C1 cassette of NR1
mRNA expression at 14, 21, and 28 days following TNBS administration. In this study, we examined the NR1
serine phosphorylation at 14 days following TNBS injection. Male Sprague-Dawley rats (200-250 g) were treated with TNBS (20mg per rat) diluted in 50%
ethanol (n=3) and vehicle controls of 50%
ethanol (n=3). TNBS and vehicle controls were administered with a 24 gauge
catheter inserted into the lumen of the rat colon. The animals were sacrificed at 14 days after induction of the
colitis and their distal colon was retrieved for two-dimensional (2D) western blot analysis.
Serine phosphorylation of the NR1 subunit with C1 cassette appears at 14 days after TNBS injection. In contrast, there was no NR1-C1 expression in the vehicle controls and untreated normal controls. These results suggest a role for colonic-
NMDA receptor phosphorylation in the development of neuronal plasticity following colonic
inflammation. Phosphorylation of NR1 may partially explain visceral
hypersensitivity present during colonic
inflammation.