Defecation Responses Research Articles

Stroboscopic lighting with intensity synchronized to rotation velocity alleviates motion sickness gastrointestinal symptoms and motor disorders in rats.

Motion sickness (MS) is caused by mismatch between conflicted motion perception produced by motion challenges and expected “internal model” of integrated motion sensory pattern formed under normal condition in the brain. Stroboscopic light could reduce MS nausea symptom via increasing fixation ability for gaze stabilization to reduce visuo-vestibular confliction triggered by distorted vision during locomotion. This study tried to clarify whether MS induced by passive motion could be alleviated by stroboscopic light with emitting rate and intensity synchronized to acceleration–deceleration phase of motion. We observed synchronized and unsynchronized stroboscopic light (SSL: 6 cycle/min; uSSL: 2, 4, and 8 cycle/min) on MS-related gastrointestinal symptoms (conditioned gaping and defecation responses), motor disorders (hypoactivity and balance disturbance), and central Fos protein expression in rats receiving Ferris wheel-like rotation (6 cycle/min). The effects of color temperature and peak light intensity were also examined. We found that SSL (6 cycle/min) significantly reduced rotation-induced conditioned gaping and defecation responses and alleviated rotation-induced decline in spontaneous locomotion activity and disruption in balance beam performance. The efficacy of SSL against MS behavioral responses was affected by peak light intensity but not color temperature. The uSSL (4 and 8 cycle/min) only released defecation but less efficiently than SSL, while uSSL (2 cycle/min) showed no beneficial effect in MS animals. SSL but not uSSL inhibited Fos protein expression in the caudal vestibular nucleus, the nucleus of solitary tract, the parabrachial nucleus, the central nucleus of amygdala, and the paraventricular nucleus of hypothalamus, while uSSL (4 and 8 cycle/min) only decreased Fos expression in the paraventricular nucleus of hypothalamus. These results suggested that stroboscopic light synchronized to motion pattern might alleviate MS gastrointestinal symptoms and motor disorders and inhibit vestibular-autonomic pathways. Our study supports the utilization of motion-synchronous stroboscopic light as a potential countermeasure against MS under abnormal motion condition in future.

S0456 Revisiting the Cut-Off for an Abnormal Balloon Expulsion Test: Can We Make Testing More User Friendly?

INTRODUCTION: Chronic constipation (CC) is a common gastrointestinal complaint in clinical practice. Anorectal Manometry (ARM), Balloon Expulsion Testing (BET), and Defecography (DEF) are used to evaluate for dyssynergic defecation (DD) in CC patients. Literature provides poor to moderate agreement between ARM, BET, and DEF. The current threshold for a normal BET is <60 seconds. This threshold, though widely adopted, has not been rigorously validated. Our aim was to determine if a shorter or longer expulsion time offers improved performance characteristics to the current cut off for an abnormal BET of <60-seconds. METHODS: A retrospective cross-sectional study was conducted on 4746 CC patients ≥18 years of age who were referred for AFT at a single tertiary-care center from July 2003 to February 2020. All CC patients underwent an ARM and BET with a sub-set completing an ARM, BET, and DEF (n = 726). Abnormal AFT were defined as the following: ARM = simulated defecation responses with ≤20% anal relaxation; BET = the inability to expel a 50 ml water-filled balloon in ≤60-seconds; DEF = paradoxical contraction, increase anorectal angle, and/or the inability to expel barium contrast. DD was defined as an abnormal ARM and DEF. Linear BET time marks were coded for an abnormal test every 30-seconds: 30–120 seconds. Sensitivity, specificity, positive predictive values (PPV), and negative predictive values (NPV) were calculated for each 30-second BET time point using an abnormal ARM, DEF, and DD as individual state variables. RESULTS: Demographics (N = 4746) were as follows: mean age 48.8 ± 16.4 years (18–93), mean BMI 27.5 ± 7.2, 81.8% female, and 85.3% Caucasian. The BET sensitivity and specificity were similar at 30, 60, 90, and 120 seconds for an abnormal ARM, DEF, and DD (Table 1). The PPV for identifying an abnormal ARM for BET using a threshold of 120 seconds (sec) = 79%, for BET 90 sec = 68.0%, BET 60 sec = 62.1%, and BET 30 sec = 47.7% (Table 1). The NPV for BET 120 sec = 27.9%, BET 90 sec = 44.6%, BET 60 sec = 50.9%, and BET 30 sec = 62.7% (Table 1). Similar profiles for PPV and NPV for abnormal DEF and DD relative to various BET time thresholds (Table 1). CONCLUSION: A BET threshold of <60 seconds offers the best combination of performance characteristics for dyssynergic defecation relative to a few different gold standards and should remain the standard for defining an abnormal BET.Table 1

Sex and Age Differences in Motion Sickness in Rats: The Correlation with Blood Hormone Responses and Neuronal Activation in the Vestibular and Autonomic Nuclei.

Many studies have demonstrated sex and age differences in motion sickness, but the underlying physiological basis is still in controversy. In the present study, we tried to investigate the potential correlates of endocrine and/or neuronal activity with sex and age differences in rats with motion sickness. LiCl-induced nausea symptom was evaluated by conditioned gaping. Motion sickness was assessed by measurement of autonomic responses (i.e., conditioned gaping and defecation responses), motor impairments (i.e., hypoactivity and balance disturbance) after Ferris wheel-like rotation, and blood hormone levels and central Fos protein expression was also observed. We found that rotation-induced conditioned gaping, defecation responses and motor disorders were significantly attenuated in middle-aged animals (13- and 14-month-age) compared with adolescents (1- and 2-month-age) and young-adults (4- and/or 5-month-age). LiCl-induced conditioned gapings were also decreased with age, but was less pronounced than rotation-induced ones. Females showed greater responses in defecation and spontaneous locomotor activity during adolescents and/or young-adult period. Blood adrenocorticotropic hormone and corticosterone significantly increased in 4-month-old males after rotation compared with static controls. No significant effect of rotation was observed in norepinephrine, epinephrine, β-endorphin and arginine-vasopressin levels. The middle-aged animals (13-month-age) also had higher number of rotation-induced Fos-labeled neurons in the spinal vestibular nucleus, the parabrachial nucleus (PBN), the central and medial nucleus of amygdala (CeA and MeA) compared with adolescents (1-month-age) and young-adults (4-month-age) and in the nucleus of solitary tract (NTS) compared with adolescents (1-month-age). Sex difference in rotation-induced Fos-labeling was observed in the PBN, the NTS, the locus ceruleus and the paraventricular hypothalamus nucleus at 4 and/or 13 months of age. These results suggested that the sex and age differences in motion sickness may not correlate with stress hormone responses and habituation. The age-dependent decline in motion sickness susceptibility might be mainly attributed to the neuronal activity changes in vestibulo-autonomic pathways contributing to homeostasis regulation during motion sickness.

Chronic stress-induced alterations in mouse colonic 5-HT and defecation responses are strain dependent

Mood disorders and chronic stress are frequently associated with gastrointestinal (GI) symptoms including diarrhoea or constipation. Locally produced serotonin [5-hydroxytryptamine (5-HT)] regulates GI motility and is a key factor in the pathophysiology of stress-associated GI disorders. We aimed to establish whether chronic stress can differentially affect faecal output and colon 5-HT concentration in two inbred mouse strains: BALB/c and C57BL/6 which differ in their ability to cope with stress. Adult male BALB/c and C57BL/6 mice were restrained for 2 h daily for 10 days. Defecation was monitored during each stress session. Twenty-four hours after the last session of stress, plasma corticosterone concentration was higher than control in both strains, indicative of a physiological effect of chronic stress; however, stress-induced diarrhoea was more persistent in C57BL/6 mice. Basal concentration of colon 5-HT was higher in C57BL/6 mice, and stress elicited an increase in colon 5-HT only in this strain. Finally, naïve BALB/c mice had a higher sensitivity (incidence of diarrhoea) to 5-HT (0.33 mg/kg, i.p.) than C57BL/6 mice. Our results suggest that differential defecation responses to stress may be associated with colon 5-HT concentration, which may in turn reflect the individual sensitivity to 5-HT. In addition, C57BL/6 mice emerge as a relevant model for studying GI alterations induced by chronic stress.

High Protein Diet Selectively Reduces Fat Mass and Improves Glucose Tolerance in Diet-Induced Obese (DIO) Rats

Background: Acute tail pinch is known to stimulate food intake (FI) in rats through opiate signaling pathways. However, the chronic effects remain to be characterized. Aim: To establish a model for acute and chronic stress-induced alterations of FI and investigate brain nuclei and neuropeptide Y (NPY)-activated pathways and changes in circulating ghrelin, adrenocorticotropic hormone (ACTH) and glucose levels. Methods: Ad libitum fed male Sprague-Dawley rats were subjected to acute (5 min) or chronic (5 min daily for 14 days) tail pinch using a clip fastened to the tail and FI was monitored. Results: Acute tail pinch strongly increased the 5-min FI compared to undisturbed rats (1.01±0.29 vs. 0.03±0.01 g/ 300g, P 0.05), whereas blood glucose was significantly elevated (131.6±5.3 vs. 108.6±3.1 mg/dl, P<0.01). Fos expression monitored 90 min after tail pinch was increased in the parvicellular paraventricular nucleus (pPVN), arcuate nucleus, locus coeruleus and the nucleus of the solitary tract. In the pPVN, 39% of the tail pinch-activated Fos-positive cells were also CRF-immunoreactive. When rats were pinched daily for 14 days, 5-min orexigenic response was the strongest during the first five days (1.6±0.0 g/300g) and reduced during the last five days (-50%, P<0.001). At the same time, 5-min fecal pellet output was increased during the last five days compared to the first five days of the experiment (+58%, P<0.05) resulting in a negative correlation of 5-min food intake and fecal pellet output (r=-0.55, P<0.05). Repeatedly pinched rats had a reduced 14-day cumulative food intake (-4%, P<0.05) and body weight gain (-22%, P<0.05) associated with lower gain of fat mass (-99%) and lean mass (-25%) compared to undisturbed controls (P<0.05). Conclusions: Acute tail pinch increases FI via neural mechanisms likely involving arcuate nucleus NPY Y1 → opioid pathways established to regulate feeding, whereas humoral signals such as ghrelin do not seem to be involved in the acute effect. The central CRF signaling system activated by acute tail pinch may predominate after chronic tail pinch which could explain the reduced FI and increased defecation responses and decreased body weight gain. Tail pinch is a suited model to study acute stress-induced eating while repeated exposure leads to decreased fat mass gain similar to other stressors.

Tail Pinch is a Model for Acute Stress-Induced Eating in Rats Through Activation of NPY Y 1 Receptors

Background: Acute tail pinch is known to stimulate food intake (FI) in rats through opiate signaling pathways. However, the chronic effects remain to be characterized. Aim: To establish a model for acute and chronic stress-induced alterations of FI and investigate brain nuclei and neuropeptide Y (NPY)-activated pathways and changes in circulating ghrelin, adrenocorticotropic hormone (ACTH) and glucose levels. Methods: Ad libitum fed male Sprague-Dawley rats were subjected to acute (5 min) or chronic (5 min daily for 14 days) tail pinch using a clip fastened to the tail and FI was monitored. Results: Acute tail pinch strongly increased the 5-min FI compared to undisturbed rats (1.01±0.29 vs. 0.03±0.01 g/ 300g, P 0.05), whereas blood glucose was significantly elevated (131.6±5.3 vs. 108.6±3.1 mg/dl, P<0.01). Fos expression monitored 90 min after tail pinch was increased in the parvicellular paraventricular nucleus (pPVN), arcuate nucleus, locus coeruleus and the nucleus of the solitary tract. In the pPVN, 39% of the tail pinch-activated Fos-positive cells were also CRF-immunoreactive. When rats were pinched daily for 14 days, 5-min orexigenic response was the strongest during the first five days (1.6±0.0 g/300g) and reduced during the last five days (-50%, P<0.001). At the same time, 5-min fecal pellet output was increased during the last five days compared to the first five days of the experiment (+58%, P<0.05) resulting in a negative correlation of 5-min food intake and fecal pellet output (r=-0.55, P<0.05). Repeatedly pinched rats had a reduced 14-day cumulative food intake (-4%, P<0.05) and body weight gain (-22%, P<0.05) associated with lower gain of fat mass (-99%) and lean mass (-25%) compared to undisturbed controls (P<0.05). Conclusions: Acute tail pinch increases FI via neural mechanisms likely involving arcuate nucleus NPY Y1 → opioid pathways established to regulate feeding, whereas humoral signals such as ghrelin do not seem to be involved in the acute effect. The central CRF signaling system activated by acute tail pinch may predominate after chronic tail pinch which could explain the reduced FI and increased defecation responses and decreased body weight gain. Tail pinch is a suited model to study acute stress-induced eating while repeated exposure leads to decreased fat mass gain similar to other stressors.

Home cage activity and behavioral performance in inbred and hybrid mice

Locomotor activity is a key component in many behavioral tests, suggesting that genetic differences in activity levels may be a critical consideration when comparing mouse strains. In order to assess the relationship between activity and performance, we recorded home cage activity, and locomotion and defecation, a non-activity-linked behavior, in tests of anxiety in inbred (C57BL/6J (B6), n=25; BALB/cJ (C), n=24; DBA/2J (D2), n=28) and hybrid (CB6F1/6J (CB6: B6×C) n=19) mice. Under our test conditions, the strains showed significant differences in home cage activity levels: C>B6>D2. The CB6 mice were similar to the B6 mice in horizontal activity and were intermediate between the parental strains in vertical movement. Based on measures of locomotion and defecation in the open field, emergence and novel object tests, and the elevated zero maze, the C mice appeared to be the most anxious and the B6 were the least anxious. The D2 mice were intermediate on some measures but more similar to B6 mice on others, making ranking them more difficult. In addition, the CB6 mice displayed characteristics of both parental strains. They had greater similarity to B6 mice in measures of horizontal movement in the home cage and locomotion in the open field and emergence tests, but exhibited defecation responses similar to those of C mice in the novel object test and elevated zero maze. The results suggest that strain differences in spontaneous locomotion should be considered when interpreting strain differences in behavioral tests, and that home cage activity may be a useful interpretive aid.

Sodium arsanilate-induced vestibular dysfunction in rats: Effects on open-field behavior and spontaneous activity in the automated digiscan monitoring system

Vestibular dysfunction was chemically induced in Long-Evans rats by intratympanic injections (30 mg per side) of sodium arsanilate (atoxyl). Following a one-week recovery period the rats were behaviorally assayed for integrity of the labyrinthine systems. All subjects were tested for presence of the air-righting reflex, the contact-righting reflex (by lightly holding a sheet of Plexiglas against the soles of the rat's feet), and body rotation-induced nystagmus. All animals were then tested for their ability to remain on a small (15 × 15 cm) platform. Next, the subjects were given two 10-min open-field tests during which ambulation, rearing, grooming, and defecation responses were recorded. Four to five weeks later all rats were tested twice (60 min per session) in the automated Digiscan Activity Monitor which provides a multivariate assessment of spontaneous motor activity. The rats with vestibular dysfunction (Group VNX) took significantly less time to fall off the platform ( p<0.01). They also exhibited significantly more open-field ambulation but fewer rearing responses ( ps<0.01). An examination of group correlation coefficients for open-field variables and the platform test scores revealed some interesting group differences ( ps<0.05). In the Digiscan tests the atoxyl-treated rats exhibited fewer number of horizontal movements, but increased speed for these movements ( ps<0.05). Vertical movements did not differ significantly in incidence, but these movements were greatly reduced in duration ( p<0.001). In general, changes in spontaneous behavior observed in the sodium arsanilate-treated rats were consistent with a loss in ability to balance on the two hind feet (during rearing or grooming) and a redirecting of exploratory vertical movement sequences toward horizontal locomotion, especially in the open-field test. The multivariate behavioral assessment available in the Digiscan Activity Monitoring system seems to be especially useful in the examination of behavioral components affected by vestibular dysfunction.

Behavioral effects of exposure to Nuclear Magnetic Resonance Imaging: I. Open-field behavior and passive avoidance learning in rats

The effect of exposure to the magnetic and radio-frequency fields associated with Nuclear Magnetic Resonance Imaging (MRI) on two standard animal behavior tests, was examined in rats. In the first experiment male rats were given a baseline open-field test and 48 hrs later exposed for 22.5 min to a MRI procedure, a sham imaging procedure, or a control condition. Immediately after this exposure period a second open-field test was administered. All animals were given 4 more daily exposures to their respective treatment conditions and after the last exposure period a third open-field test was given. Analysis of open-field ambulation, rearing, and defecation responses indicated no significant effect of exposure to MRI on these behaviours. In a second experiment rats were conditioned in a step-down passive avoidance task and then exposed for 23.2 min (48 hrs later) to MRI, sham imaging, or control conditions. Retention tests for the passive avoidance response were administered after the first and fifth daily exposure to the experimental treatment conditions. No significant effects of the treatment conditions on retention of the avoidance response were obtained and a third retention test 3 months after the second test, also failed to provide any evidence for treatment effects. These results fail to provide any evidence for short or long term behavioral changes in animals exposed to MRI.

The principle of aggregation in psychobiological correlational research: An example from the open-field test

The principle of aggregation states that the sum of a set of multiple measurements is a more stable and representative estimator than any single measurement. This greater representation occurs because there is inevitably some error associated with measurement. By combining numerous exemplars, such errors of measurement are averaged out, leaving a clearer view of underlying relationships. The present study explored the effect of score aggregation over various time periods on correlations among a number of reliable measures frequently used in open-field testing. Twenty-six male rats were given four open-field tests (4 min in duration) at 48-h intervals. Ambulation, rearing, and defecation responses were measured on a minute-by-minute basis in the open-field tests. Correlation matrices were calculated among the three measures for unaggregated scores (1-min totals) and for scores aggregated over daily tests, and mean correlation coefficients were computed for all three pairwise comparisons of the three response variables. These mean correlations were then compared to those obtained when the open-field measures were aggregated over all 4 test days. The results showed that aggregation produced substantial increases in correlation-coefficient magnitude. The correlation between ambulation and rearing increased from a mean of .39 to a value of .81. Similar increases were observed when defecation scores were correlated with ambulation (−.17 to −.59) and rearing (−.16 to −.49). Thus aggregation is an important factor to be considered in the design of psychobiological correlational studies.

Investigatory behavior in snakes, II: Cage cleaning and the induction of defecation in snakes

In Experiment 1, boid and colubrid snakes defecated with shorter latencies after their home cages were cleaned than did control snakes that received equivalent handling without cage cleaning. Experiment 2 replicated this finding and also showed that snakes exposed to clean cages emit more tongue flicks after reintroduction to the clean home cage than do control snakes. Experiment 3 demonstrated that cage cleaning has similar effects in two species of crotalid snakes. The increase in tongue flicking after cage cleaning is interpreted as investigatory behavior and reflects the fact that snakes respond to the absence of familiar odors. Experiment 4 showed that a clean cage containing odors derived from snake feces produces less tone-flick exploration and fewer defecation responses in rattlesnakes than does a clean cage without such odors.

Alpha-MSH- and novelty-induced emotional responses in rats: associated changes in plasma corticosterone and brain catecholamines.

In a series of experiments it was demonstrated that defecation responses induced in rats by exposure to novel environments did not habituate if the animals were treated with alpha-melanocyte stimulating hormone (alpha-MSH). The MSH-treated rats sustained high defecation responses on 6 successive days of exposure, whereas control rats habituated. The role of plasma 11-hydroxycorticosterone (11-OHCS) levels and brain catecholamines (CAs) in this novelty-induced defecation following alpha-MSH administration was also investigated. Baseline studies showed that MSH treatment alone increased plasma 11-OHCS levels in the resting condition and lowered brain dopamine (DA) but not norepinephrine (NE) concentrations. It was found, however, that plasma 11-OHCS levels in MSH-treated rats were not significantly increased on successive days of combined MSH and novelty treatments but that whole brain DA and NE concentrations were both lowered. A strong negative correlation was observed between defecation responses and brain DA concentrations on successive days of the joint MSH and novelty treatment. In all the experiments alpha-MSH treatment had no effect on step-down activity.

Effects of melanocyte-stimulating hormone (MSH) and melatonin on passive avoidance and on an emotional response

The present experiment investigated the opposite effects of synthetic α-MSH and Melatonin on acquisition and extinction of a passive avoidance response (PAR) and on emotionality, as indexed by defecation, in the PA box. It was found that intraperitoneal (IP) administration of α-MSH delayed extinction and increased defecation responses whereas IP administration of Melatonin facilitated extinction of the PAR and decreased defecation. The present experiment confirmed MSH-Melatonin opposition on memory and on the defecation response.

Effect of intraventricularly administered prostaglandin E1 on the electrical activity of cerebral cortex and behavior in the unanesthetized monkey

Effect of PGE1 administered into anterior horn of lateral cerebral ventricle of unanesthetized monkey on changes of behavior and electrical activity of ipsilateral prefrontal cerebral cortex was studied. PGE1 in doses of about 50 μg/kg body weight caused tremor, disturbance of posture, catatonia and stupor for several minutes followed later by somnolence. The monkey also made occasional vocalizations during the phase of motor disturbance. Micturition and defecation responses also occurred. The electroencephalogram was desynchronized. Further, the rate of spontaneous discharge of impulses of some of the neurons of the prefrontal cortex was markedly decreased, up to about 33% of control. During the state of depression of spontaneous activity, the neuron could still be evoked to activity by electrical stimulation of dorsomedial thalamic nucleus. The duration of short latency negative wave evoked in the depth of the cortex by electrical stimulation of dorsomedial thalamus was not decreased but augmented under PGE1. This indicated that the decrease of spontaneous activity of the neurons under PGE1 could not be due to a postsynaptic inhibition of the neurons but probably due to alterations caused somewhere in the presynaptic chain. Low doses (about 25 μg/kg body weight) of PGE1 have not caused any disturbances of movements or posture, but caused drowsiness and facilitated sleep behavior. The results are discussed on the basis of previous reports on effects of PGE1 on adrenergic synaptic transmission in nervious system.

Emotional Behavior and Adrenal Function in the Rat

The relationship of open-field behaviors (latency, ambulation, rearing, and defecation) and adrenal weight and adrenal ascorbic acid (AAA) was investigated. 38 male Sprague-Dawley rats received one daily trial in the open field for 4 days. Measures of adrenal weight and AAA were subsequently obtained. Correlations between variables indicated no meaningful relationship between emotional defecation and adrenal responses. Rearing correlated significantly with AAA. Latency was significantly related with adrenal weight. These results are consistent with recent studies investigating performance of emotional Ss on escape-avoidance conditioning and CER behavior.