Effects of two different acute and subchronic stressors on gastrointestinal transit in the rat: A radiographic analysis

Abstract

Background:The reaction to stress is an adaptive response necessary for survival.When stressors are repeated, the organism adapts, although these adaptive responses can become dysregulated and result in disease, causing gastrointestinal (GI) disorders.Radiographic methods allow the non-invasive study of how a given factor affects GI transit in the same animal at different time points. These methods have never been applied to study the consequences of stress on GI motor function and their dependency on time and stimulus. Therefore, our aim was to characterize, using radiographic techniques, the effect on GI transit of cold-restraint (CR) and forced swim (FS) stress applied acutely and subchronically in the rat.Methods: Male Wistar rats (260-330 g) were submitted to FS or CR stress, during 1 (acute) or 4 (subchronic) consecutive days. To study GI transit, radiographic methods were used. Radiographs were taken 0-24 h after barium intragastric administration on the 1st or 4th day of stress, which was applied 1 h after contrast.Results: Acute FS or CR slowed down gastric and small intestinal emptying but had opposite effects in the caecum: CR tended to accelerate barium transit and feces formation while FS tended to slow these parameters down. When the stimuli were applied subchronically, GI transit was not completely normalized in most of the studied parameters. Conclusion and Inferences:Mild stress alters GI transit differently depending on the nature of the stressor and its duration. Exposure to mild stressors should be considered as contributing factors to different functional GI disorders.

Short-term stress significantly decreases morphine analgesia in trigeminal but not in spinal innervated areas in rats

“…Overall, we did not find any effect of stress on GI transit; previous studies have shown that GI motility tends to normalize when homotypic stress is applied [2]. Curiously, there was a slight delay in the transit of the small intestine, which is in line with our previous study, although the time of stress induction is different in both studies [59]. Nevertheless, FSS did not modify the effect of morphine on GI motility.…”

Radiographic assessment of the impact of sex and the circadian rhythm-dependent behaviour on gastrointestinal transit in the rat

“…Since radiopacity is measured using the average of all faecal pellets, the decrease at T24 is a reflection of the production of new pellets (without staining) during the night, when animals are more active and also eat more. 20–22…”

“…In this sense, food ingestion increases during the phase of activity, which corresponds to the lights off period. 20 Although fasting is usually imposed in gastrointestinal transit studies and its duration has an impact on the results, 11 in the present study we did not fast the animals before the experiments for ethical reasons (fasting duration would have been much longer than 24 h). Therefore, manipulation, which was the same for all animals, was limited to the unavoidable handling of the animals needed to take the X-rays.…”

“…Since radiopacity is measured using the average of all faecal pellets, the decrease at T24 is a reflection of the production of new pellets (without staining) during the night, when animals are more active and also eat more. [20][21][22] The increased moisture (associated with highest wet faecal matter expulsion; Supplementary Figure S3(b)) of the faecal pellets collected at T1 (Figure 4(d)) probably reflects some level of psychological stress, since increased faecal moisture and faecal production are generally considered as indirect markers of stress in male rats. 23 # p < 0.05, ## p < 0.01, ### p < 0.001, #### p < 0.0001 vs. M-N; $$$ p < 0.001, $$$$ p < 0.0001 vs. M-I; *p < 0.05, ****p < 0.0001 vs. F-N (two-way analysis of variance followed by Tukey post-hoc test).…”

“…These results were expected, since in the M-I group the experiments performed from T0 to T8 occur during their activity phase, when animals move, eat and defecate more. [20][21][22]39 Interestingly, the moisture of the faecal pellets did not increase at T1 in M-I as seen for M-N, suggesting that during their activity phase the males might be less sensitive to the stress produced by the new experimental conditions (transport to the X-ray room, barium gavage, brief restraint . .…”