The effects of adolescent methylphenidate self-administration on responding for a conditioned reward, amphetamine-induced locomotor activity, and neuronal activation. 2010

Christie L Burton, and José N Nobrega, and Paul J Fletcher
Department of Psychology, University of Toronto, 100 St. George Street, Toronto, ON M5S3G3, Canada. c.burton@utoronto.ca

BACKGROUND Abuse of methylphenidate (Ritalin) is rising, particularly during adolescence and early adulthood, but the long-term effects of its abuse during adolescence are unclear. METHODS In experiment 1, we examined the effect of adolescent methylphenidate self-administration (0.0625 mg/infusion), as compared with cocaine self-administration (0.125 mg/infusion), under a fixed ratio 1 schedule of reinforcement in male Sprague-Dawley rats during adolescence (postnatal day (PND) 32-47) on adult dopamine-mediated behaviors (PND >70). These included responding for a conditioned reward (CR), a measure of incentive motivation, and amphetamine-induced locomotor activity. In experiment 2, we aimed to replicate and enhance the effects observed in experiment 1, and we also examined the effects of methylphenidate self-administration during adolescence on adult amphetamine-induced zif268 messenger ribonucleic acid (mRNA) expression. RESULTS Adolescent rats self-administered both cocaine and methylphenidate. There was no effect of adolescent drug self-administration on adult baseline or amphetamine-induced responding for a CR. However, both adolescent methylphenidate and cocaine self-administration increased amphetamine-induced locomotion. Adolescent methylphenidate self-administration also enhanced amphetamine-induced zif268 mRNA expression in the nucleus accumbens. CONCLUSIONS Our findings suggest that repeated, behaviorally contingent exposure to methylphenidate during adolescence enhances responsivity to the locomotor-stimulating and neuronal activating effects of amphetamine but not incentive motivation.

UI MeSH Term Description Entries
D008297 Male Males
D008774 Methylphenidate A central nervous system stimulant used most commonly in the treatment of ATTENTION DEFICIT DISORDER in children and for NARCOLEPSY. Its mechanisms appear to be similar to those of DEXTROAMPHETAMINE. The d-isomer of this drug is referred to as DEXMETHYLPHENIDATE HYDROCHLORIDE. Centedrin,Concerta,Daytrana,Equasym,Metadate,Methylin,Methylphenidate Hydrochloride,Phenidylate,Ritalin,Ritalin-SR,Ritaline,Tsentedrin,Hydrochloride, Methylphenidate,Ritalin SR
D009043 Motor Activity Body movements of a human or an animal as a behavioral phenomenon. Activities, Motor,Activity, Motor,Motor Activities
D009474 Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM. Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D009714 Nucleus Accumbens Collection of pleomorphic cells in the caudal part of the anterior horn of the LATERAL VENTRICLE, in the region of the OLFACTORY TUBERCLE, lying between the head of the CAUDATE NUCLEUS and the ANTERIOR PERFORATED SUBSTANCE. It is part of the so-called VENTRAL STRIATUM, a composite structure considered part of the BASAL GANGLIA. Accumbens Nucleus,Nucleus Accumbens Septi,Accumbens Septi, Nucleus,Accumbens Septus, Nucleus,Accumbens, Nucleus,Nucleus Accumbens Septus,Nucleus, Accumbens,Septi, Nucleus Accumbens,Septus, Nucleus Accumbens
D012055 Reinforcement Schedule A schedule prescribing when the subject is to be reinforced or rewarded in terms of temporal interval in psychological experiments. The schedule may be continuous or intermittent. Reinforcement Schedules,Schedule, Reinforcement,Schedules, Reinforcement
D003042 Cocaine An alkaloid ester extracted from the leaves of plants including coca. It is a local anesthetic and vasoconstrictor and is clinically used for that purpose, particularly in the eye, ear, nose, and throat. It also has powerful central nervous system effects similar to the amphetamines and is a drug of abuse. Cocaine, like amphetamines, acts by multiple mechanisms on brain catecholaminergic neurons; the mechanism of its reinforcing effects is thought to involve inhibition of dopamine uptake. Cocaine HCl,Cocaine Hydrochloride,HCl, Cocaine,Hydrochloride, Cocaine
D003216 Conditioning, Operant Learning situations in which the sequence responses of the subject are instrumental in producing reinforcement. When the correct response occurs, which involves the selection from among a repertoire of responses, the subject is immediately reinforced. Instrumental Learning,Learning, Instrumental,Operant Conditioning,Conditionings, Operant,Instrumental Learnings,Learnings, Instrumental,Operant Conditionings
D000367 Age Factors Age as a constituent element or influence contributing to the production of a result. It may be applicable to the cause or the effect of a circumstance. It is used with human or animal concepts but should be differentiated from AGING, a physiological process, and TIME FACTORS which refers only to the passage of time. Age Reporting,Age Factor,Factor, Age,Factors, Age
D000661 Amphetamine A powerful central nervous system stimulant and sympathomimetic. Amphetamine has multiple mechanisms of action including blocking uptake of adrenergics and dopamine, stimulation of release of monamines, and inhibiting monoamine oxidase. Amphetamine is also a drug of abuse and a psychotomimetic. The l- and the d,l-forms are included here. The l-form has less central nervous system activity but stronger cardiovascular effects. The d-form is DEXTROAMPHETAMINE. Desoxynorephedrin,Levoamphetamine,Phenopromin,l-Amphetamine,Amfetamine,Amphetamine Sulfate,Amphetamine Sulfate (2:1),Centramina,Fenamine,Mydrial,Phenamine,Thyramine,levo-Amphetamine,Sulfate, Amphetamine,l Amphetamine,levo Amphetamine

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