Self-administration of the Dopamine D3 Agonist 7-OH-DPAT in Rhesus Monkeys Is Modified by Prior Cocaine Exposure

Psychopharmacology (Berl). 1996 May;125(1):13-22. doi: 10.1007/BF02247388.

Abstract

Cocaine self-administration was compared with responding maintained by the dopamine D3 agonist 7-hydroxy-N,N-di-n-propyl-2-aminotetralin (7-OH-DPAT) in rhesus monkeys. In the first experiment, monkeys (n = 3) with an extensive cocaine history responded under a fixed-interval (FI) 5-min schedule of IV cocaine (0.03 mg/kg per injection) presentation, during daily 4-h sessions. When responding was stable, dose-response curves were determined for cocaine (0.01-0.3 mg/kg per injection) and 7-OH-DPAT (0.001-0.1 mg/kg per injection); each dose was available for at least five consecutive sessions. When substituted for the baseline dose of cocaine, other doses of cocaine and 7-OH-DPAT maintained rates higher than responding maintained by saline injections, in all monkeys. 7-OH-DPAT maintained response rates equal to or higher than rates of cocaine-maintained responding in all monkeys. In a second experiment, acquisition of 7-OH-DPAT self-administration was evaluated in a group of cocaine-naive monkeys (n = 3). Various doses of 7-OH-DPAT (0.003-0.03 mg/kg per injection) were available under an FI 15-s schedule during daily 4-h sessions. After 10-13 sessions, 7-OH-DPAT self-administration could not be trained in any cocaine-naive monkey. When cocaine was made available to these monkeys, responding was reliably maintained within one to four sessions and the schedule was gradually increased to FI 5-min. After stable responding under an FI 5-min schedule of 0.03 mg/kg per injection cocaine presentation, 7-OH-DPAT (0.01 mg/kg per injection) was again made available to two of the monkeys, and maintained responding at rates higher than saline. To determine better whether a history of responding maintained by another reinforcer would result in high rates of 7-OH-DPAT self-administration, two cocaine-naive monkeys were trained to respond under an FI 5-min schedule of food presentation. Substituting 7-OH-DPAT (0.003-0.03 mg/kg per injection) for food resulted in very low rates of responding. Taken together, these results suggest that despite comparable reinforcing effects in cocaine-substitution studies, 7-OH-DPAT and cocaine differ in their rate of acquisition, perhaps indicating a lower abuse liability for 7-OH-DPAT.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Behavior, Animal / drug effects*
  • Cocaine / pharmacology*
  • Dopamine Agonists / pharmacology*
  • Dose-Response Relationship, Drug
  • Female
  • Macaca mulatta
  • Male
  • Self Administration
  • Tetrahydronaphthalenes / pharmacology*

Substances

  • Dopamine Agonists
  • Tetrahydronaphthalenes
  • Cocaine
  • 7-hydroxy-2-N,N-dipropylaminotetralin