Biomedical subjects

Ricardo Pellón

Publications and source records attributed to Ricardo Pellón.

4 recordsLinked to original sources

PubMed2007

Pharmacological analysis of the effects of benzodiazepines on punished schedule-induced polydipsia in rats.

Food-deprived Wistar rats were exposed to a fixed-time 60-s food delivery schedule until they developed schedule-induced polydipsia. Every fifth lick was then followed by an electric shock during two, signalled, 5-min periods, which ran concurrently with the food delivery schedule. Shock intensities were adjusted to reduce licking to 60-70% of the unpunished licking rates. The benzodiazepine full agonists, diazepam (0.3-3.0 mg/kg), chlordiazepoxide (0.3-10.0 mg/kg), oxazepam (0.3-3.0 mg/kg) and the benzodiazepine partial agonist, RU-32698 (3.0-17.0 mg/kg), led to increases in punished responding at intermediate doses and decreases at the highest doses tested. All benzodiazepine agonists brought about dose-dependent decreases in unpunished schedule-induced polydipsia, with doses required to reduce drinking proving higher than doses required to increase punished schedule-induced polydipsia. The antipunishment effect of 0.3 mg/kg of diazepam was dose-dependently antagonized by flumazenil and the benzodiazepine inverse agonist, RU-34000. Flumazenil effects, however, could reflect actions of flumazenil as a partial inverse agonist at GABAA receptors. RU-32698 at 10.0 mg/kg further facilitated the rate-increasing effect of 0.3 mg/kg of diazepam, but at 17.0 mg/kg partially blocked such antipunishment effect. Overall, the present results extend the similarities of the effects of benzodiazepine compounds on adjunctive and operant patterns of behaviour by showing similar interactions within the benzodiazepine receptor complex.

Animals↗

PubMed2006

Level of response suppression and amphetamine effects on negatively punished adjunctive licking.

The purpose of the present study was to investigate whether the level of response suppression is a major determinant of the effect of D-amphetamine on negatively punished adjunctive drinking. Rats were initially exposed to a multiple fixed-time (FT) 30-s FT 30-s food delivery schedule. They were then divided into two groups and subjected to one of two different multiple schedules, FT 30-s FT 45-s or FT 30-s FT 90-s. The FT 45-s and FT 90-s components were signalled by a tone. Comparably high levels of adjunctive licking were observed in both FT 30-s components, intermediate licking levels in the FT 45-s component, and little licking in the FT 90-s component. Licking during the FT 30-s components was subsequently punished by lick-contingent signalled delays (by a blackout) in food delivery. The duration of such delays was adjusted to reduce licking to levels obtained in the FT 45-s or FT 90-s components, respectively for each of the two groups. Punished licking was increased by 0.3 and 1.0 mg/kg of D-amphetamine, an effect that was greater in the FT 30-s FT 90-s group. No increase in licking was observed in the FT 45-s component, but the 1.0 mg/kg dose also increased responding in the FT 90-s component. In general, no statistically significant differences were found between the effects of D-amphetamine on punished and unpunished schedule-induced licking. As licking decreased during the FT 90-s component when the punishment contingency was introduced in the alternate component, the punishment procedure and FT 30-s component were entirely removed. On this occasion, D-amphetamine failed to increase licking induced by the FT 90-s schedule. These results indicate that the level of response suppression might be a good indicator of the degree to which D-amphetamine shows antipunishment effects on adjunctive licking reduced by negative punishment procedures.

Animals↗

PubMed2004

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

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.

Animals↗

PubMed2003

Amphetamine increases schedule-induced drinking reduced by negative punishment procedures.

RATIONALE: d-Amphetamine has been reported to increase schedule-induced drinking punished by lick-dependent signalled delays in food delivery. This might reflect a drug-behaviour interaction dependent on the type of punisher, because no such effect has been found when drinking was reduced by lick-contingent electric shocks. However, the anti-punishment effect of amphetamine could be mediated by other behavioural processes, such as a loss of discriminative control or an increase in the value of delayed reinforcers. OBJECTIVES: To test the effects of d-amphetamine on the acquisition and maintenance of schedule-induced drinking reduced by unsignalled delays in food delivery. METHODS: Rats received 10-s unsignalled delays initiated by each lick after polydipsia was induced by a fixed-time 30-s food reinforcement schedule or from the outset of the experiment. Yoked-control rats received these same delays but independently of their own behaviour. d-Amphetamine (0.1-3.0 mg/kg) was then tested IP. RESULTS: d-Amphetamine dose-dependently increased and then decreased punished schedule-induced drinking. The drug led to dose-dependent reductions when the delays were not contingent or when they were applied from the outset of training. CONCLUSIONS: These results support the contention that d-amphetamine has an increasing effect on schedule-induced drinking that has been previously reduced by a negative punishment procedure. This effect cannot be attributed to other potentially involved processes, and therefore support the idea that drug effects on punished behaviour depend on punishment being delays in food or shock deliveries.

Animals↗