The effects of Fructus Aurantii extract on the 5-hydroxytryptamine and vasoactive intestinal peptide contents of the rat gastrointestinal tract.

CONTEXT

Fructus Aurantii, the unripe fruit of Citrus aurantium Linn (Rutaceae), is a Qi-regulating drug used in traditional Chinese medicine to improve gastrointestinal (GI) function. Vasoactive intestinal peptide (VIP) and 5-hydroxytryptamine (5-HT) regulate GI motility and fluid secretion.

OBJECTIVE

We tested whether the Fructus Aurantii extract altered VIP and 5-HT expression levels in rats.

MATERIALS AND METHODS

Experimental rats were administered 0.3 g/ml Fructus Aurantii water decoction at 2.0 ml/100 g body weight per day for 10 days by gavage feeding, while control rats were gavage fed equal volumes of distilled water. Expression levels of 5-HT and VIP were measured by immunohistochemical staining and microscopic image analysis of the GI mucosa and myenteric nerve plexus.

RESULTS

Average 5-HT staining intensity scores in the stomach antrum, duodenal mucosa and jejunal mucosa were significantly higher in the Fructus Aurantii treatment group than in the control group (antrum: 213% of control; duodenum: 193%; jejunum: 256%; p < 0.05 for all). In contrast, the average VIP density scores in the stomach antrum, duodenal mucosa and jejunal mucosa were significantly lower in the Fructus Aurantii group (antrum: 14% of control; duodenum: 15%; jejunum: 38%; p < 0.01 for all). Tissues from Fructus Aurantii-treated rats exhibited significantly greater numbers of 5-HT- and VIP-immunopositive cells in the gastric antrum, duodenum and jejunum mucosal layer but fewer VIP-expressing cells in the myenteric nerve plexus (p < 0.05 for both).

CONCLUSION

Fructus Aurantii can enhance gastrointestinal motility by altering 5-HT and VIP expression levels in the rat GI tract.