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Biomedical subjects

P. Willner

Publications and source records attributed to P. Willner.

10 recordsLinked to original sources
PubMed1996

Effects of mood manipulation on subjective and behavioural measures of cigarette craving.

Cigarette cravings were evaluated in a sample of moderately heavy smokers, using the Questionnaire on Smoking Urges (QSU), and a progressive-ratio (PR) operant procedure in which responding on a computer keyboard was reinforced by puffs on a cigarette, under a progressively increasing work requirement. Subjects were also exposed to musical mood-induction procedures: the induction and maintenance of depressed and elated mood states was confirmed by visual analogue scales and a mood questionnaire. Smoking did not alter mood state. However, relative to the elated condition, induction of a depressed mood caused increases in both QSU scores and measures of PR performance. The results provide the first experimental confirmation of a causal relationship between depressed mood and cigarette craving.

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PubMed1995

Effects of reinforcer sweetness and the D2/D3 antagonist raclopride on progressive ratio operant performance.

Previous studies have reported that DA receptor antagonists suppress most behaviours; however, a paradoxical increase in performance may be seen in tests of operant or consummatory behaviours maintained by very sweet rewards, which lie on the descending limb of the inverted U-shaped concentration-performance function (i.e., under conditions where performance decreases as sweetness increases). Despite the low performance levels associated with very sweet reinforcers, preference studies indicate that they are nonetheless more rewarding. In the present study, the hypothesis that reinforcer efficacy is monotonically related to reinforcer sweetness was tested using a geometric progressive ratio reinforcement schedule, in which increasing numbers of responses were required to earn successive reinforcers (1, 2, 4, 8,.); the amount of work the animal emits in order to obtain an increasingly infrequent reinforcer is assumed to provide a measure of the magnitude of its rewarding effect. Three groups of rats were trained on this schedule, using as reinforcers food pellets containing 1%, 10% and 95% sucrose, respectively. Under conditions of continuous sucrose-pellet reinforcement, the highest response rates were maintained by the 10% sucrose pellets. However, under the progressive ratio schedule, performance was monotonically related to sucrose concentration. The dopamine D2/D3 receptor antagonist raclopride dose-dependently suppressed progressive ratio performance in all three groups.

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PubMed1992

Environmental influences on behavioural sensitization to the dopamine agonist quinpirole.

A runway was used to measure locomotor responses to quinpirole (200µg/kg), in rats. The locomotor stimulant effect of quinpirole increased progressively over successive trials at 3-day intervals. Animals administered quinpirole in the home cage were also sensitized, but to a lesser degree than animals tested in the runway following quinpirole injections. Exposure to an open field, following quinpirole injections, sensitized responsiveness in the runway to an extent comparable to that seen following runway exposure. Animals exposed to a movable running wheel, following quinpirole injections, were more sensitized to the effect of quinpirole in the runway than animals exposed to a locked running wheel. The results suggest that the extent of sensitization to quinpirole is determined by the behaviour elicited by the drug, rather than the environment in which it is administered. An operant conditioning model is proposed to account for these effects.

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PubMed1991

Differential effects of d-fenfluramine, l-fenfluramine and d-amphetamine on the microstructure of human eating behaviour.

An observational technique, demonstrated to provide reliable data under a variety of conditions, was used to evaluate the effects of d-fenfluramine, l-fenfluramine, d-amphetamine, and fenfluramine-amphetamine combinations on eating behaviour in human subjects. Following an overnight fast, subjects ate lunch from a dispenser allowing free access to a choice of ten sweet and savoury foods, of varying macronutrient composition. D-fenfluramine (30mg) and d-amphetamine (15mg) reduced food intake; l-fenfluramine (30mg) was essentially inactive. The net effects of d-fenfluramine and d-amphetamine on food intake were additive, but the behavioural mechanisms of action were different for the two drugs. D-amphetamine decreased the duration of the meal, as well as the time spent chewing or manipulating food and the number of bites, but had no effect on eating rate; by contrast, d-fenfluramine decreased the rate of eating, but had no effect on meal duration.

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PubMed1991

Anatomical substrates for neuroleptic-induced reward attenuation and neuroleptic-induced response decrement.

Rats were implanted with bilateral indwelling cannulae, in the nucleus accumbens (NAS), anterodorsal striatum (ADS) or basolateral amygdala (BLA). Administration of sulpiride to the NAS reduced spontaneous locomotion, caused a time-independent suppression of lever pressing on a random-interval 30sec schedule of food reinforcement, and reduced preference for a weak 0.7% sucrose solution over water without affecting the total volume of fluid consumed. Administration of sulpiride to the ADS did not affect spontaneous locomotion, but caused a time-dependent response decrement in both operant behaviour and consumption of 0.7% sucrose. Administration of sulpiride to the BLA had no effect in any of these tests. However, at all three infusion sites, sulpiride increased the consumption of a 34% sucrose solution. The data suggest a preferential involvement of the mesolimbic dopamine system in neurolepticinduced attenuation of reinforcer value, and a primary role of the nigrostriatal dopamine system in neuroleptic-induced time-dependent response decrements.

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PubMed1989

Effects of isolated housing and chronic antidepressant treatment on cooperative social behaviour in rats.

Pair-housed, water-deprived rats were trained to run in a two-way shuttle box, using water reinforcement. Animals were tested either singly or in pairs; in the paired condition, the animals were required to shuttle in close physical proximity. Paired performance, but not single performance was severely disrupted by single housing for 3-7 weeks. Performance of singly-housed animals could be restored either by re-housing in pairs (30 days) or by chronic (30 day) treatment with the antidepressants imipramine or fluoxetine. Chronic imipramine was also prophylactically active in preventing the deterioration in performance of singly-housed animals. The superior paired performance of pair-housed animals and of imipramine-treated singly-housed animals, was abolished by the 5-HT antagonist metergoline. Metergoline had relatively little effect on single running: the DA antagonist pimozide disrupted paired and single running equally. The results suggest a role for 5-HT in cooperative performance and in the action of antidepressant drugs in this paradigm.

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PubMed1989

Time-dependent and schedule-dependent effects of dopamine receptor blockade.

Rats were trained on one of two multiple random-interval schedules of reinforcement, which contained both ascending and descending reinforcement density sequences. The design of the schedules made it possible to determine whether performance changes in a particular component depended on the reinforcement density in that component, or on its temporal position within the schedule. Performance impairments following administration of the dopamine D1 antagonist SCH-23390 were both time- and schedule-dependent: SCH-23390 caused a relatively greater suppression of poorly reinforced responding that increased over time. The results, which are compatible with data on the effects of dopamine antagonists in other behavioural paradigms, illustrate the methodological problems of using Herrnstein's matching equation to interpret time-dependent behavioural changes.

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