Environmental modulation of cocaine self-administration in the rat.
BACKGROUND
Previous studies have shown that environmental context can powerfully modulate the induction of psychomotor sensitization to cocaine in the rat. Rats that receive repeated administrations of cocaine in association with environmental novelty exhibit greater psychomotor sensitization than animals that receive the same treatments in their home cages.


OBJECTIVE
The goal of the present study was to investigate whether environmental context can exert its modulatory influence also on cocaine self-administration.


METHODS
Independent groups of rats with intravenous catheters were given the possibility to self-administer different doses of cocaine (0.0, 0.2, 0.4, and 0.8 mg/kg per infusion) under two environmental conditions. Some animals were housed in the self-administration cages (home groups), whereas other rats were transported to the self-administration cages only for the test sessions (novelty groups).


RESULTS
Environmental "novelty" facilitated the acquisition of cocaine self-administration at the doses of 0.2 and 0.4 mg/kg per infusion. When rats were given access to a higher dose of cocaine (0.8 mg/kg per infusion), there were no significant group differences in drug taking. Environmental context had no effect on the self-administration of the vehicle. Thus, it appears that environmental "novelty" produced a shift to the left in the dose-effect curve for cocaine self-administration. Furthermore, "novelty" enhanced the motivation of the rats to work for cocaine, as indicated by the results of a progressive ratio procedure.


CONCLUSIONS
The present findings demonstrate for the first time that the environment surrounding drug taking can alter both the intake of and motivation for cocaine.
Caprioli
Daniele
D
Department of Human Physiology and Pharmacology, University of Rome Sapienza, 5 Piazzale Aldo Moro, 00185, Rome, Italy.
Paolone
Giovanna
G
Celentano
Michele
M
Testa
Arianna
A
Nencini
Paolo
P
Badiani
Aldo
A
D000818:Animals; D016739:Behavior, Addictive / Q000523:psychology; D003042:Cocaine / Q000008:administration & dosage* / Q000494:pharmacology; D018765:Dopamine Uptake Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004777:Environment; D007262:Infusions, Intravenous; D008297:Male; D009042:Motivation; D011597:Psychomotor Performance / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012055:Reinforcement Schedule; D012201:Reward; D012646:Self Administration / Q000523:psychology*
D018765:Dopamine Uptake Inhibitors; D003042:Cocaine