Acquisition of IV amphetamine and cocaine self-administration in rats as a function of dose

Marilyn E Carroll, Sylvie T. Lac

Research output: Contribution to journalArticlepeer-review

110 Scopus citations

Abstract

The effect of dose on the acquisition of IV amphetamine and cocaine self administration was examined. Three unit doses of amphetamine (0.03, 0.06 and 0.12 mg/kg) and three unit doses of cocaine (0.05, 0.2 and 0.8 mg/kg) were tested in separate groups of ten (amphetamine) or 13 (cocaine) rats. Autoshaping methods were used to train rats to press a lever that resulted in drug infusion under a fixed-ratio (FR) 1 schedule. A dally 6-h autoshaping component non-contingently delivered 60 infusions according to a 60-s random time schedule with ten infusions delivered during the first half of each h. Each day autoshaping sessions were followed by a 6-h self administration session. The criterion for acquisition was a 5-day period during which a daily mean of 100, 50 or 25 infusions for the three amphetamine doses and 400, 100 or 25 infusions were earned during the 6-h self-administration period for the three cocaine doses, respectively. As dose increased, more rats per group acquired drug self-administration arid the mean number of days to meet the acquisition criterion decreased. The percentage of rats acquiring amphetamine self-administration increased with dose and ranged from 80 to 100%. Only one rat at the lowest cocaine dose met the acquisition criterion, but 100 percent of the rats at the two higher doses acquired. During the last 2 days of acquisition, mean infusions decreased and mean drug intake (mg/kg) increased as dose increased. On the last day of acquisition, the time course of infusions during the 6-h self-administration component was characterized by a steady rate of infusions per hour, and number of infusions was inversely related to dose. These findings indicate that the initial available dose of a drug is an important determinant of the rate and probability that successful acquisition will occur.

Original languageEnglish (US)
Pages (from-to)206-214
Number of pages9
JournalPsychopharmacology
Volume129
Issue number3
DOIs
StatePublished - Jan 1 1997

Keywords

  • Acquisition
  • Amphetamine
  • Autoshaping
  • Cocaine
  • Dose
  • IV intake
  • Rats
  • Self-administration

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