Schedule-induced defecation: No-food and massed-food baselines

Reatividade ao automonitoramento em uma portadora da síndrome do intestino irritável

O automonitoramento (AM) é usado para a observação, avaliação e intervenção em problemas comportamentais e de saúde. Neste estudo, utilizou-se AM na avaliação de comportamentos de uma mulher de 44 anos de idade com a síndrome do intestino irritável (SII). Durante um período de 19 semanas a paciente preencheu formulários diários de AM de atividades diárias, sintomas intestinais e consumo alimentar. Uma melhora não programada nos sintomas foi observada, que pode ser explicada como um efeito de reatividade ao AM. Inicialmente as atividades diárias da paciente aconteciam de forma ininterrupta e eram associadas à constipação intestinal; com a ajuda de AM ela aprendeu a realizar interrupções dessas atividades quando dos sinais de motilidade intestinal, aumentando assim a frequência de evacuação.

Captopril alters schedule induced polydipsia, urination, and defecation in rats

Schedule induced polydipsia, urination and defecation were examined in rats that received training on a fixed interval 2 min schedule of food reinforcement. In Phase I of the experiment, animals received peripheral injections of captopril (an angiotensin conversion enzyme blocker, 0.5 or 50 mg/kg), or equivalent volumes of 0.9% saline. The results showed that low doses of captopril (0.5 mg/kg) significantly increased both operant responding and the adjunctive behaviors. High peripheral doses of captopril significantly reduced responding and schedule induced behavior. In Phase II of the experiment, animals received either low peripheral doses of captopril (sc 0.5 mg/kg), or low doses that were coupled with central injections (i.e., 0.12 mg icv + 0.5 mg/kg sc). As observed in Phase I, low peripheral doses of captopril enhanced behavior, but the enhancement effect was eliminated with low (0.12 mg) central administration. The overall results are consistent with past research examining captopril effects on non-operant, meal-induced drinking. Yet since captopril affected operant responding and adjunctive behaviors similarly, the findings suggest that angiotensin plays a common role in the motivational processes that precede and follow the arrival of food.

Failure to induce defecation in rats exposed to fixed-time schedules of liquid food delivery

Previous studies have found that defecation increases in rats exposed to fixed-time schedules of dry food delivery. The purpose of the present study was to examine whether increases in defecation could be induced in rats exposed to fixed-time schedules of liquid food delivery. Eight rats were exposed to fixed-time 30-, 60-, and 120-s schedules of liquid food delivery. None of the subjects excreted significantly more fecal boli under the fixed-time schedules than during massed-food control sessions in which an equivalent amount of food was presented at the beginning of the sessions. Thus, the present findings identify a previously unknown constraint on schedule-induced defecation in rats.

The effects of d-amphetamine and diazepam on schedule-induced defecation in rats

The effects of d-amphetamine (0.32 to 5.6 mg/kg) and diazepam (0.10 to 5.6 mg/kg) on defecation were examined in two groups of rats. One group was exposed to a fixed-time 60-s (FT 60-s) schedule of food delivery and the other group was exposed to massed-food sessions. During vehicle control sessions, rats exposed to the FT 60-s schedule excreted a significantly higher number of fecal boli than rats exposed to massed-food sessions. d-Amphetamine, at doses above 0.56 mg/kg, significantly reduced defecation (boli produced) in both groups, although the magnitude of the drug's effect was larger in the group exposed to the FT 60-s schedule. For both groups, diazepam only produced a significant decrease in defecation at the highest dose (5.6 mg/kg). These results appear to be inconsistent with interpretations of adjunctive behavior that emphasize arousal or emotion as mechanisms.

Assessment of stereotypic and self-injurious behavior as adjunctive responses

Certain responses of both humans and nonhumans appear to be maintained indirectly by intermittent reinforcement schedules and have been referred to collectively as adjunctive behavior. Although basic research has examined adjunctive behavior extensively, relatively few studies have been conducted with humans, particularly those with developmental disabilities who often engage in frequent and varied stereotypic behavior. This study assessed possible adjunctive characteristics of self-injurious and stereotypic behaviors using a multielement design containing two types of control conditions. Four subjects who engaged in both self-injurious behavior and stereotypy participated after variables maintaining their self-injury were identified via functional analyses. Each day, subjects were exposed to three 15-min sessions in random order: (a) noncontingent presentation of food on a fixed-time schedule (e.g., FT 30 s), (b) a massed-reinforcement (food) control, and (c) a no-reinforcement control. A variety of fixed-time schedules were examined during different experimental phases. Results of this preliminary study suggested that self-injury was not induced by intermittent reinforcement schedules, whereas the stereotypic behavior of some individuals showed characteristics of adjunctive behavior. The importance of research on adjunctive behavior and suggestions for future studies are discussed.

Schedule-induced defecation by rats during ratio and interval schedules of food reinforcement

Lever pressing in rats was maintained by continuous and intermittent schedules of food while defecation was monitored. In Experiment 1, reinforcement densities were matched across variable-ratio and variable-interval schedules for three pairs of rats. Defecation occurred in all 3 rats on the variable-ratio schedule and in all 3 rats on the yoked variable-interval schedule. In Experiment 2, fixed-ratio and fixed-interval schedules with similar reinforcement densities maintained lever pressing. Defecation occurred in 3 of 4 rats on the fixed-ratio schedule and in 4 of 4 rats on the fixed-interval schedule. Almost no defecation occurred during continuous reinforcement in either experiment. These results demonstrate that defecation may occur during both ratio and interval schedules and that the inter-reinforcement interval is more important than the behavioral requirements of the schedule in generating schedule-induced defecation.