Gastrointestinal dysfunction in a Parkinson's disease rat model and the changes of dopaminergic, nitric oxidergic, and cholinergic neurotransmitters in myenteric plexus. J Mol Neurosci. 2012;47:15-25. [PMID: 21647710 DOI: 10.1007/s12031-012-9723-7]

Expression of dopamine D2 receptor in the gastrointestinal mucosa of rats with slow transit constipation

AIM: To investigate the expression of dopamine D2 receptor (Drd2) in the gastrointestinal mucosa of rats with slow transit constipation (STC) to explore the possible pathogenesis of STC.

METHODS: Twenty-four healthy Wistar rats were randomly into two groups: an experiment group and a control group. Rats of the experiment group were daily administered diphenoxylate (8 mg/kg) for 90 d to induce STC, while the control rats were fed normal saline. The number and weight of fecal granules and the body weight of rats were recorded every 5 d. After successful induction of STC, the rats were killed to take tissues of the gastric antrum, small intestine, and colon. Real-time polymerase chain reaction (RT-PCR) was used to detect the expression of Drd2 in the above tissues.

RESULTS: The daily number and mean weight of fecal granules and the time to discharge of the first black granule differed significantly between the two groups, suggesting that STC was successfully induced. Drd2 was specifically amplified by RT-PCR. Compared with the control group, the expression of Drd2 in the stomach and small intestine was not significantly different in the experiment group (P > 0.05 for both). However, the expression of Drd2 in colon tissues of STC rats was significantly higher than that in control rats (1.93 ± 0.78, P < 0.05).

CONCLUSION: The expression of Drd2 in the stomach and small intestine does not change significantly in STC rats, but Drd2 expression is up-regulated in colon tissues of STC rats, which may contribute to the pathogenesis of STC.