Effects of oral administration of ondansetron, a 5-HT3 receptor antagonist, on anxiety-related behaviors and colonic hypercontractility in repeated stress-induced mice.

PURPOSE: Chronic psychological stress develops and exacerbates irritable bowel syndrome (IBS). 5-hydroxytryptamine (5-HT) via activation of intestinal 5-HT3 receptors involves impairment of intestinal functions. This study aimed to investigate the effects of ondansetron, a 5-HT3 receptor antagonist, on locomotor activity, anxiety-related behaviors, and colonic functions in repeated water avoidance stress. MATERIALS AND METHODS: Food intake and fecal pellet output (FPO) of sham stress (SS), water avoidance stress (WS), and water avoidance stress with oral administration of ondansetron (1 mg/kg BW) (WA) groups were monitored along the water avoidance stress protocol for 10 consecutive days. On day 11, locomotor activity and anxiety-related behaviors were determined using an open field test. Contractile properties of colonic tissues in response to KCl and a cumulative dose of carbachol (CCh) were determined using in vitro organ bath technique. RESULTS: FPO was significantly increased in the WS group after 7 days of water avoidance stress, which was reversed in WA group. WS group decreased unsupported rearing behavior compared to WS group, which was not altered in the WA group. The colon of the WS group had a higher tonic contraction in response to CCh than the SS and WA groups, which was reversed with ondansetron pre-incubation. CONCLUSIONS: Oral administration of ondansetron prevented increased FPO but did not affect anxiety-related behavior in repeated stress model. Colonic hypercontractility in the stressed mice was related to increased responses to cholinergic-induced contractions, which involved 5-HT3 receptors. Our findings suggest the modulatory roles of 5-HT3 receptors to mediate stress-induced colonic dysfunction.

5-HT3 receptors modulate changes in voiding pattern and bladder contractility in water avoidance stress-induced bladder overactivity in male mice.

PURPOSE: Chronic psychological stress aggravates painful bladder syndrome symptoms. Previous studies suggest roles of 5-HT3 receptors in regulating micturition and bladder hypersensitivity. This study aimed to investigate the roles of 5-HT3 receptors in modulating voiding patterns and spontaneous bladder contractile properties in water avoidance stress-induced mice. MATERIALS AND METHODS: Voiding patterns in sham stress (SS), water avoidance stress (WS), and water avoidance stress with daily oral gavage of ondansetron (1 mg/kg BW) (WA) groups were analyzed after exposure to repeated water avoidance stress for 10 days. Changes in contractile activity of isolated bladder in response to KCl, carbachol, and 5-hydroxytryptamine were determined. Bladder mast cell quantification was examined using toluidine blue staining. RESULTS: Urine voided area was significantly decreased in WS group after exposure to 10 days of the stress protocol, which was reversed in the WA group. The WS group had a higher number of urine spots than the SS group. Increased mast cell degranulation was observed in the stressed mice. Bladder strips of the WS group showed higher tonic and amplitude of spontaneous contraction than the SS group, which were normalized by ondansetron administration. Increased response to carbachol-induced bladder contraction was observed in the bladder of stressed mice, which was attenuated with ondansetron pre-incubation. CONCLUSIONS: Water avoidance stress-induced mice exhibited changes in voiding pattern, which was reversed by oral administration with a 5-HT3 receptor antagonist (ondansetron). Enhanced contractile response to cholinergic stimulation in the urinary bladder of the psychological stress-induced bladder overactivity was mediated through 5-HT3 receptors.