Enhanced colonic peristalsis by impairment of nitrergic enteric neurons inspontaneously diabetic rats

Changes in enteric neurons containing various neurotransmitters in the colo n have been described in diabetic rats; however, how these changes are rela ted to colonic motility disorders remains unclear. Nitric oxide (NO) is kno wn to be an important inhibitory neurotransmitter in the enteric nervous sy stem. In the present study, we investigated the peristaltic reflex using ou r modified Trendelenburg's method to evaluate the differences in enteric ni trergic neurons of the distal colon between spontaneously diabetic rats and their sibling control rats. We measured maximum intraluminal pressure, thr eshold pressure and propagation distance of the reflex contraction. These d iabetic rats showed a greater maximum intraluminal pressure than that in th e control rats. N-G-nitro-L-arginine methyl ester (L-NAME) significantly in creased the maximum pressure in the control rats. Although L-arginine did n ot change the maximum pressure, sodium nitroprusside (SNP) significantly de creased it in these diabetic rats. Nicotinamide adenine dinucleotide phosph ate (NADPH) diaphorase reactivities in the myenteric plexus were much weake r in the diabetic rats than those in the control rats. These results indica te that the colonic peristaltic reflex is enhanced by impairment of enteric nitrergic inhibitory neurons in spontaneously diabetic rats. (C) 2001 Else vier Science B.V. All rights reserved.