Controlled ingestion of kaolinite (5%) modulates enteric nitrergic innervation in rats
Résumé
We have previously shown that kaolinite slowed down gastric emptying and intesti- nal transit and induced changes in enteric mechanical activities. As gastric emptying and intestinal transit have been shown to be regulated by nitric oxide (NO), the effect of an imposed ingestion of kaolinite on enteric nitrergic innervation was determined. Kaolinite has also been shown to increase plasmatic levels of leptin. Therefore, the responses of enteric neurons in the presence of leptin after kaolinite ingestion were determined, and a possible role of nitrergic neurons was evaluated in rats using organ bath technique. Our results showed that kaolinite modulates activities of enteric nerves at 14 days of ingestion. Exogenous L-NNA produced a decrease in nerve stimulation (NS)-induced relaxation in both jejunum and colon of control groups. At 14 days of kaolinite ingestion, this effect of L-NNA was significantly reduced only in the jejunum. Although L-NNA did not affect NS-induced contraction in jejunum and colon of control animals, it increased the amplitude of the NS- induced contraction in the colon of rats at 14 days of kaolinite ingestion. Leptin inhibitory effects on ENS in the jejunum were also altered at 14 days of ingestion. These differences were masked in the presence of L-NNA. Our data give evidence that changes in mechanical activities induced by kaolinite might be due to alterations in inhibitory (nitrergic and/or other) innervation at 14 days of kaolinite ingestion and to modifications of leptin effects on the responses to intramural nerve stimulation.