Food In Female Rats Research Articles

Extended vs. brief intermittent access to palatable food differently promote binge-like intake and rejection of less preferred food in female rats

Extended vs. brief intermittent access to palatable food differently promote binge-like intake and rejection of less preferred food in female rats

Neonatal environmental intervention alters the vulnerability to the metabolic effects of chronic palatable diet exposure in adulthood

Previous studies have demonstrated that early environmental interventions influence the consumption of palatable food and the abdominal fat deposition in female rats chronically exposed to a highly caloric diet in adulthood. In this study, we verified the metabolic effects of chronic exposure to a highly palatable diet, and determine the response to its withdrawal in adult neonatally handled and non-handled rats. Consumption of foods (standard lab chow and chocolate), body weight gain, abdominal fat deposition, plasma triglycerides, and leptin, as well as serum butyrylcholinesterase (BuChE), and cerebral acetylcholinesterase (AChE) activities were measured during chronic chocolate exposure and after deprivation of this palatable food in female rats exposed or not to neonatal handling (10 minutes/day, 10 first days of life). Handled rats increased rebound chocolate consumption in comparison to non-handled animals after 1 week of chocolate withdrawal; these animals also decreased body weight in the first 24 hours but this effect disappeared after 7 days of withdrawal. Chocolate increased abdominal fat in non-handled females, and this effect remained after 30 days of withdrawal; no differences in plasma leptin were seen after 7 days of withdrawal. Chocolate also increased serum BuChE activity in non-handled females, this effect was still evident after 7 days of withdrawal, but it disappeared after 30 days of withdrawal. Chocolate deprivation decreased cerebral AChE activity in both handled and non-handled animals. These findings suggest that neonatal handling modulates the preference for palatable food and induces a specific metabolic response that may be more adaptive in comparison to non-handled rats.

RESEARCH FOCUS ON COMPULSIVE BEHAVIOUR IN ANIMALS: Pre‐exposure to environmental cues predictive of food availability elicits hypothalamic–pituitary–adrenal axis activation and increases operant responding for food in female rats

The present study was undertaken to develop an animal model exploiting food cue-induced increased motivation to obtain food under operant self-administration conditions. To demonstrate the predictive validity of the model, rimonabant, fluoxetine, sibutramine and topiramate, administered 1 hour before the experiment, were tested. For 5 days, female Wistar rats were trained to self-administer standard 45 mg food pellets in one daily session (30 minutes) under FR1 (fixed ratio 1) schedule of reinforcement. Rats were then trained to an FR3 schedule and finally divided into two groups. The first group (control) was subjected to a standard 30 minutes FR3 food self-administration session. The second group was exposed to five presentations of levers and light for 10 seconds each (every 3 minutes in 15 minutes total). At the completion of this pre-session phase, a normal 30-minute session (as in the control group) started. Results showed that pre-exposure to environmental stimuli associated to food deliveries increased response for food when the session started. Corticosterone and adrenocorticotropic hormone plasma levels, measured after the 15-minute pre-exposure, were also significantly increased. No changes were observed for the other measured hormones (growth hormone, prolactin, thyroid-stimulating hormone, luteinizing hormone, insulin, amylin, gastric inhibitor polypeptide, ghrelin, leptin, peptide YY and pancreatic polypeptide). Rimonabant, sibutramine and fluoxetine significantly reduced food intake in both animals pre-exposed and in those not pre-exposed to food-associated cues. Topiramate selectively reduced feeding only in pre-exposed rats. The present study describes the development of a new animal model to investigate cue-induced increased motivation to obtain food. This model shows face and predictive validity, thus, supporting its usefulness in the investigation of new potential treatments of binge-related eating disorders. In addition, the present findings confirm that topiramate may represent an important pharmacotherapeutic approach to binge-related eating.

Neonatal isolation enhances acquisition of cocaine self-administration and food responding in female rats

We showed previously that neonatal isolation (ISO) enhances acquisition of cocaine self-administration in adult male rats without altering acquisition of food responding. Female rats show poorer performance in learning tasks and are differentially affected by stress compared to male rats. Thus, we investigated whether ISO alters acquisition of operant responding for cocaine and food in female rats with comparison to male rats. Litters were subjected to ISO or were non-handled (NH). Activity levels were assessed in adult rats. Then, rats were implanted with jugular catheters and allowed to self-administer cocaine under a fixed-ratio 1 (FR1) schedule of reinforcement using an escalating dose presentation procedure. Cocaine intake, discrimination of active versus inactive levers, and ineffective active lever responses were tabulated. Effects of non-contingent cocaine infusions (primes) and increasing FR on responding were then assessed. Other rats were allowed to lever press for food under an FR1 schedule (10 s time-out). ISO enhanced acquisition of operant responding for food and cocaine in female rats. The latter was demonstrated by better lever discrimination, emission of fewer ineffective responses, and superior performance in response to primes. Yet, NH females ingested more cocaine than ISO females during the initial acquisition phase. In male rats, ISO enhanced acquisition of cocaine self-administration but not food responding. Activity levels were unaffected by ISO or gender. These data confirm and extend our previous findings demonstrating the enduring effects of ISO on adult self-administration behavior and emphasize the importance of measuring behavioral patterns versus intake in acquisition studies.