Fluid intake and behavioral changes in rats associated with the distension of the small and large intestine

Irritable bowel syndrome (IBS): could we decide what is behind?

Functional visceral problems are frequently present nowadays in the medical practice probably due to the significant mental and emotional load on people. Although physicians and psychophysiologists are active on the field, still we are far from a complete knowledge, despite the fact that scientists like the Hungarian Professor György Ádám already had initiated a new approach called visceral psychophysiology already a long time ago. In this article, we commemorate Professor Ádám by analyzing one of the most frequent functional disorders, irritable bowel syndrome (IBS), calling psychophysiology for help. First, we try to give a definition, then show the general descriptions and characteristics of IBS. Factors like stress, gender, and gastrointestinal pain are followed by the potential role of the immune system and the neuronal factors as well as the supposed brain mechanisms. We hope that this overview of the IBS-history would show how significant scientists can be decisive in certain fields of the science and practice.

Early oral feeding versus nasojejunal early enteral nutrition in patients following pancreaticoduodenectomy: a propensity score-weighted analysis of 428 consecutive patients

BACKGROUND

Notwithstanding that significant medical progress has been achieved in recent years, the optimal nutritional support method following pancreaticoduodenectomy (PD) remains uncertain. This study compared the safety and feasibility of early oral feeding (EOF) with nasojejunal early enteral nutrition (NJEEN) after PD.

METHODS

A retrospective cohort study was conducted on 428 consecutive patients who underwent PD between August 2018 and December 2020. During the first study phase, the routine postoperative feeding strategy was NJEEN, later replaced by EOF during the second study phase. The primary outcome was the incidence of delayed gastric emptying (DGE) following PD. Propensity score weighting was used to control for confounding factors.

RESULTS

Four hundred forty patients underwent PD during the overall study period, with 438 patients aged 18 years and older. Ten patients experienced accidental tube dislodgement or migration and were excluded from the study based on the exclusion criteria. Finally, 211 patients and 217 patients underwent EOF and NJEEN, respectively. After propensity score weighting, it was observed that patients who underwent postoperative EOF experienced a significantly lower DGE (B/C) rate compared to those who underwent postoperative NJEEN [7.38% (31/424) vs. 14.97% (62/413), P =0.0005]. Subgroup analyses according to the presence of soft pancreatic texture yielded consistent results. The EOF group exhibited lower DGE grade, DGE (B/C) rate [5.90% (11/194) vs. 22.07% (43/193), P <0.0001], postoperative gastrointestinal endoscopic intervention rate, and Clavien-Dindo Grade III or higher rate.

CONCLUSIONS

EOF is superior to NJEEN in reducing the incidence of grade B/C DGE after PD. The EOF procedure is safe and feasible and should be recommended as the optimal postoperative feeding method following PD.

Early Nasojejunal Nutrition Versus Early Oral Feeding in Patients After Pancreaticoduodenectomy: A Randomized Controlled Trial

Objective

The aim of this study was to test the hypothesis that early oral feeding (EOF) is superior to early nasojejunal nutrition (ENN) after pylorus-preserving pancreaticoduodenectomy (PPPD) in terms of delayed gastric emptying (DGE).

Background

DGE is a common complication after PPPD. Although EOF after PPPD is recommended by several international guidelines, there is no randomized trial to support this recommendation.

Methods

From September 2016 to December 2017, a total of 120 patients undergoing PPPD were randomized into the ENN, EOF, or saline groups at a 1:1:1 ratio (40 patients in each group). The primary endpoint was the rate of clinically relevant DGE. Secondary endpoints included overall morbidity, postoperative pancreatic fistula, post-pancreatectomy hemorrhage, abdominal infection, length of hospital stay, reoperation rate, and in-hospital mortality.

Results

The baseline characteristics and operative parameters were comparable between the groups. The incidence of clinically relevant DGE varied significantly among the three groups (ENN, 17.5%; EOF, 10.0%; saline, 32.5%; p =0.038). The saline group had a higher clinically relevant DGE rate than the EOF group (p = 0.014). The saline group also had greater overall morbidities than the ENN and EOF groups (p = 0.041 and p = 0.006, respectively). There were no significant differences in other surgical complication rates or postoperative hospital stay. No mortality was observed in any of the groups.

Conclusions

Nutritional support methods were not related to DGE after PPPD. EOF was feasible and safe after PPPD, and additional ENN should not be routinely administered to patients after PPPD.

Clinical Trial Registration

ClinicalTrials.gov, identifier NCT03150615.

Duodenal pain and spinal morphine induce conditioned taste aversion in rats

Conditioned taste aversion (CTA) is a behavioural response essential to the survival of an individual. The combination of taste and odour of most foods provides a strong conditioned stimulus (CS) for an animal to respond in an appropriate way to any harmful unconditioned stimuli (US) that follow. The most widely used conditioned stimuli are drinkable sweet solutions, such as saccharin and sucrose. CTA-like responses are also found for environmental unconditioned stimuli, but these usually take longer training. In the present study, the aversive nature of a duodenal distention with an implanted balloon catheter was studied in freely moving rats using either CTA against a sucrose solution, or a light-dark passive avoidance (PA) paradigm. In addition, the effect of spinal morphine on CTA and the cardiovascular response to duodenal distention were studied. CTA could be induced by a single, but long-lasting 20-minute duodenal distention, which did not induce PA behaviour in a light-dark box. Spinal infusion of morphine alone induced CTA, suggesting that the model is unsuitable to investigate spinal pharmacological modulation of visceral pain. Spinal morphine did reduce the cardiovascular response to duodenal distention, strengthening its validity as a visceral pain model. Since CTA is a complicating factor in the field of chemotherapy in cancer patients and spinal morphine causes nausea and vomiting in humans, CTA may also complicate spinal drug treatment or anaesthesia.

Dose-dependent effects of peptide YY(3-36) on conditioned taste aversion in rats

We used a conditioned taste aversion test to assess whether PYY(3-36) reduces food intake by producing malaise. Two-hour IV infusion of PYY(3-36) (8, 15, and 30 pmol/kg/min) at dark onset in non-food-deprived rats produced a dose-dependent inhibition of feeding and a conditioned aversion to the flavored chow paired with PYY(3-36) infusion. In food-deprived rats, PYY(3-36) at 2 and 4 pmol/kg/min inhibited intake of a flavored saccharin solution without producing conditioned taste aversion, whereas higher doses (8 and 15 pmol/kg/min) inhibited saccharin intake and produced taste aversion. These results suggest that anorexic doses of PYY(3-36) may produce a dose-dependent malaise in rats, which is similar to that reported for PYY(3-36) infusion in humans. Previous studies have shown that PYY(3-36) potently inhibits gastric emptying, and that gut distention can produce a conditioned taste aversion. Thus, PYY(3-36) may produce conditioned taste aversion in part by slowing gastric emptying.

The relationship between food reward and satiation revisited

The postingestive satiating action of food is often viewed as producing a positive affective state that rewards eating. However, in an early test of this idea, Van Vort and Smith [Physiol. Behav. 30 (1983) 279] reported that rats did not learn to prefer a food that was "real-fed" and satiating over a food that was "sham-fed" and not satiating. Subsequent investigators obtained similar findings with concentrated nutrient sources. With dilute nutrient sources, however, rats learned to prefer the real-fed to the sham-fed food. These and other findings demonstrate that nutrients have rewarding postingestive effects that enhance food preferences via a conditioning process. These reward effects appear separate from the satiating actions of nutrients, which may actually reduce food reward. Food intake and preference are controlled by a complex interaction of positive and negative signals generated by nutrients in the mouth and at postingestive sites.

Discomfort: not pain but still unpleasant feelings from the gut

Most of the factors initiating food or fluid intake have already been studied, but much less is known about those terminating ingestion. We have hypothesised that discomfort originating from the gastrointestinal system may be one of those factors. Gut distension cause pain if the intestinal volume changes but merely discomfort if only the tension of the gut wall increases. It seems that mild unpleasantness (i.e. discomfort) arising from the gut as a result of moderate (quasi-isometric) distension, among and in concordance with other factors, may significantly reduce intake and hence contribute to physiological satiety. The arising discomfort can be detected by measuring the amount and rate of the ingestion, by recording and analysing ingestive behavior by taste-aversivity and taste-reactivity tests, etc. Conclusions of all experiments point to the same direction: tension increase in the gut wall causes discomfort and results in decrease of intake, i.e. satiety.

Conditioned taste aversion to gut distension in rats

The aim of this work was to study the negative effects of the intestinal stimulation by a method that is sensitive to assess internal malaise and discomfort. Effects of volumetric and "isometric" gut distension on the behavior were compared in the small and the large intestines, respectively. Chronically separated (Thiry-Vella) intestinal loops prepared from the upper jejunum and/or from the uppermost segment of the colon were stimulated with a rubber balloon. Conditioned taste aversion (CTA) series were accompanied with recording satiety and aversive behavioral indexes. Both isometric and volumetric stimuli elicited taste aversion. No essential differences between the two intestinal parts were found. Behavioral indices supported intake data: satiety indexes were similar to each other, whereas aversive indexes were high during stimulation and lower during testing. Data were consistent over conditions and time, proving the reliability of the method. Results are compared to earlier taste reactivity records.

Modulation of taste reactivity by intestinal distension in rats

Discomfort created by intestinal distension may play a role in controlling intake behavior. We analyzed these effects in details by the taste reactivity test in Long-Evans rats. A balloon inserted into a separated Thiry-Vella intestinal loop was distended with different volumes of water (0.05, 0.09, 0.12, and 0.28 mL, respectively). Saccharin solution (0.001 M) was infused into the mouth via an implanted oral cannula nine times for 30 s, with 5-min intertrial intervals. The balloon was distended after the second and released following the seventh trial. Taste reactivity (TR) elements were videotaped and later analyzed for appetitive and aversive responses. The number of appetitive responses decreased after gut distension, whereas aversive elements were infrequent and stable. It is suggested that pleasantness of the taste stimulus decreased independently of the discomfort, which remained mild but steady; that is, sweet taste gradually lost its hedonic value but was not accompanied by an acquired aversion of the same taste. This finding may point to the difference of the motivational and discriminative effects of the internal stimuli.

Morphological and functional changes after benzalkonium chloride treatment of the small intestinal Thiry-Vella loop in rats

The aim of this work was to study the effects of benzalkonium chloride (BAC) treatment on the small intestine and its functioning in rats surgically prepared with Thiry-Vella intestinal loop. The loops were treated with either BAC, which ablated much of the myenteric plexus and extrinsic innervation, or with physiological saline (SAL). In vivo drinking experiments were performed to examine the effect on fluid intake and behavioral indices of distending the loop with a balloon. Spontaneous motility and its changes induced by acetylcholine (ACh) and histamine (His) were studied on isolated stripes in vitro. Finally, samples from the loops were examined histologically. Though reduction of the cell number was less than expected and no differences of the thickness of the muscular layer between the two groups was observed, BAC treatment altered the pattern of spontaneous activity and also the sensitivity to ACh and His in isolated stripes. In vivo distension of the SAL-treated loops reduced fluid intake and produced signs of aversivity; these effects were absent in the BAC-treated group. Our results show that despite the differences in the degree of ablation from those obtained by others, BAC treatment can be used to study the mechanisms underlying the effects of the enteral stimuli on the behavior.