Impulsive choice and environmental enrichment: Effects of d-amphetamine and methylphenidate

Jennifer L. Perry, Dustin J. Stairs, Michael T. Bardo

Research output: Contribution to journalArticlepeer-review

109 Scopus citations

Abstract

Individual differences in impulsive choice and rearing in differential environments are factors that predict vulnerability to drug abuse. The present study determined if rearing influences impulsive choice, and if d-amphetamine or methylphenidate alters impulsive choice in differentially reared rats. Male Sprague-Dawley rats were raised from 21 days of age in either an enriched condition (EC) or an isolated condition (IC) and were tested as young adults on an adjusting delay task. In this task, two levers were available and a response on one lever yielded one 45 mg food pellet immediately, whereas a response on the other yielded three pellets after an adjusting delay. The delay was initially set at 6 s, and it decreased or increased by 1 s following responses on the immediate or delayed levers, respectively. A mean adjusted delay (MAD) was calculated upon completion of each daily session, and it served as the quantitative measure of impulsivity. Once MADs stabilized, rats were injected with saline, d-amphetamine (0.5, 1.0, or 2.0 mg/kg, s.c.), or methylphenidate (2.5, 5.0, or 10.0 mg/kg, s.c.) 15 min prior to adjusting delay sessions. EC rats had higher baseline MADs (were less impulsive) than IC rats. Additionally, administration of d-amphetamine, but not methylphenidate, dose-dependently increased impulsive choice (decreased MADs) in EC rats. In IC rats, d-amphetamine and methylphenidate dose-dependently decreased impulsivity (increased MADs). These results indicate that rearing environment influences impulsive choice and moderates the effect of psychostimulants on impulsive choice. Specifically, psychostimulants may decrease environment-dependent impulsive choice in individuals with high levels of impulsivity (e.g., those with ADHD), whereas they may increase impulsive choice in individuals with low levels of impulsivity.

Original languageEnglish
Pages (from-to)48-54
Number of pages7
JournalBehavioural Brain Research
Volume193
Issue number1
DOIs
StatePublished - Nov 3 2008

Bibliographical note

Funding Information:
The authors would like to thank Blake Dennis, Josh Cutshall, and Jason Ross for technical assistance, and Jason Ross for helpful comments on earlier drafts of this manuscript. This research was funded by USPHS grants DA05312 and DA12964 (MTB) and DA07304 (JLP).

Keywords

  • Amphetamine
  • Delay discounting
  • Environmental enrichment
  • Impulsive choice
  • Individual differences
  • Methylphenidate

ASJC Scopus subject areas

  • Behavioral Neuroscience

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