Acquisition of schedule-induced polydipsia by rats in proximity to upcoming food delivery

Abstract

Food-deprived rats that receive intermittent delivery of small amounts of food develop excessive drinking--specifically, schedule-induced polydipsia (SIP). A main characteristic of SIP is its occurrence at the beginning of interfood intervals. The purpose of this study was to demonstrate that SIP can be developed toward the end of interfood intervals, in closer proximity to upcoming than to preceding food delivery. In Experiment 1, two groups were exposed to a fixed-time (FT) 30-sec food schedule with water available during the first or the last 15 sec of each interfood interval. Two additional groups, which had access to water throughout, were exposed to FT 30-sec or FT 15-sec schedules of food presentation. The FT 30-sec group with free access to water developed the highest level of intake; similar and intermediate levels were induced in all the remaining groups. In Experiment 2, three groups of rats were exposed to an FT 90-sec food schedule with water available during the first, the second, or the last 30 sec of each interfood interval. One additional group with access to water throughout was exposed to the FT 90-sec schedule of food presentation. The group with free access to water developed a higher level of consumption than did the other groups, but by the end of training none of the four groups showed statistical differences in polydipsic drinking. Results show that adjunctive drinking can be developed in proximity to upcoming food delivery even with long interfood intervals.

Adjunctive behaviors are operants

“…The left panel of Fig. 1 shows the mean rate of schedule-induced drinking by Wistar rats on schedules of periodic feeding when food was delayed by 15 or 30 s from the last touch of the drinking spout (from López-Crespo, Rodríguez, Pellón, & Flores, 2004). Similar data have been reported by Cope, Sanger and Blackman (1976).…”

“…The top curve is from a noncontingent FT 30-s food schedule, and the diamonds from an FT 15-s schedule. The crossed squares show drinking when water was never available during the last 15 s of the interval (López-Crespo et al, 2004). Contrasting the last with the top curve shows that the reduction of proximity with reinforcement decreases the level of SIP.…”

Effort-related functions of nucleus accumbens dopamine and associated forebrain circuits

“…Exposing animals to scheduled non-contingent presentation of reinforcers such as food can induce various activities, including locomotion, drinking, licking, and wheel-running (Falk 1971;Staddon and Simmelhag 1971;Killeen 1975;Killeen et al 1978;Lopez-Crespo et al 2004). Considerable evidence indicates that mesolimbic DA is involved in schedule-induced activity.…”

Schedule-induced polydipsia as a model of compulsive behavior: neuropharmacological and neuroendocrine bases

“…This excessive drinking, induced in food-deprived animals (80-85% from free feeding) and known as SIP, has been proposed as a prototype of adjunctive behavior and is unrelated to normal thirst or homeostatic needs, generally following an inverted-U-shaped pattern occurring immediately after the delivery of food (Falk 1961(Falk , 1971. Although different factors, such as the state of food deprivation or the interfood interval length reproduced by different fixed time (FT) or fixed interval (FI) schedules, influence the acquisition and expression of adjunctive drinking in SIP (Falk 1966a(Falk , 1971Flores and Pellón 1995;Flory 1971;Killeen 1970;López-Crespo et al 2004), data from our laboratory have shown that the optimal FT interval for inducing a high rate of drinking behavior is FT-30s (Cardona et al 2006) and FT-60s (López-Grancha et al 2006aMoreno et al 2010). The main variables measured during SIP are: (a) total amount of water (milliliters) removed from the bottle, (b) total number of licks, and (c) and total number of nose pokes in the food magazine.…”