Abstract:

Objective To study the role of 5-HT_3/4 receptor in the endogenous dopamine-regulated gastric motility in rats, and investigate the mechanism of the gastroparesis in Parkinson's disease. Methods Substantia nigra dopaminergic neurons of the SD rats were damaged by injecting 6-hydroxydopamine(6-OHDA) in the brain substantia nigra. In this 6-OHDA treated rat model, the central dopamine content decreased while the endogenous gastrointestinal dopamine content was increased. The power lab signal acquisition system was used to record the constriction of the strip of rat gastric longitudinal muscle. Semi-quantitative RT-PCR method and Western blotting analysis for 5-HT_3/4 receptor in the gastric corpus in control and 6-OHDA treated rats were performed. Results The basal gastric motility in 6-OHDA treated rats was significantly weaker than the control group. 5-HT-evoked motility was significantly reduced in the amplitude of contraction in 6-OHDA treated rats. The real-time PCR results showed that the mRNA level of 5-HT_3/4 receptors in the gastric corpus was significantly enhanced in 6-OHDA treated rats. The Western blotting results however showed that the protein level of 5-HT₄ receptor, not 5-HT₃ receptor, in the gastric corpus was descent in 6-OHDA treated rats. Conclusion The 5-HT₄ receptor downregulation may contribute to the decrease of gastric motility in 6-OHDA treated rats.

Key words: 5-HT_3/4 receptor, gastric motility, 6-OHDA treated rats