Effect of environmental enrichment on escalation of cocaine self-administration in rats
- First Online:
- 321 Downloads
Previous studies found that environmental enrichment protects against the initiation of stimulant self-administration in rats, but it is unclear if enrichment also protects against the escalation of stimulant use with long-term exposure.
The current study examined the effects of environmental enrichment on escalation of cocaine self-administration using an extended access procedure.
Rats were raised from 21 days in an enriched condition (EC) with social cohorts and novel objects, a social condition with only social cohorts (SC), a novelty condition (NC) with novel objects in isolated cages, or an isolated condition (IC) without social cohorts or novel objects. In young adulthood, EC, SC, NC, and IC rats were separated into short access (ShA) or long access (LgA) groups that received either 1 or 6 h, respectively, of daily cocaine self-administration (0.1 mg/kg/infusion) for 14 days. In a second experiment, EC and IC rats were used to assess differences in acquisition and escalation of cocaine self-administration at a 0.5 mg/kg/infusion unit dose.
With ShA sessions, EC rats acquired cocaine self-administration at a slower rate than IC rats at both unit doses; however, with extended training, both groups eventually reached similar rates. At the 0.1 mg/kg/infusion dose, only NC and IC rats escalated in amount of intake when switched to the LgA sessions. At the 0.5 mg/kg/infusion dose, rates of cocaine self-administration escalated in LgA groups over 14 days regardless of EC or IC rearing condition; however, EC rats escalated at a faster rate, eventually reaching the same level of intake observed in IC rats.
Although environmental enrichment protects against escalation of a low unit dose of cocaine, it may not protect against escalation with a higher unit dose. In addition, at a lower unit dose, this protective mechanism appears to be due to the presence of social cohorts rather than novel objects.
KeywordsEnvironmental enrichment Escalation Cocaine Addiction
- Adams J, Bowman K, Burke B, Casson L, Caviness L, Coffey LE (1999) National household survey on drug abuse data collection. Final reportGoogle Scholar
- Ahmed SH (2009) Escalation of drug use. In: Olmstead MC (ed) Neuromethods: animal models of drug addiction. Humana, TotowaGoogle Scholar
- Bardo MT, Valone JM, Robinet PM, Shaw WB, Dwoskin LP (1999) Environmental enrichment enhances the stimulant effect of intravenous amphetamine: search for a cellular mechanism in the nucleus accumbens. Psychobiology 27(2):292–299Google Scholar
- Carroll ME (1996) Reducing drug abuse by enriching the environment with alternative nondrug reinforcers. In: Green L, Kagel J (eds) Advances in behavioral economics. Ablex, Norwood, p 3Google Scholar
- Carroll ME, Meisch RA (1984) Increased drug-reinforced behavior due to food deprivation. In: Thompson T, Barrett JE (eds) Advances in behavioral pharmacology, 4th edn. Academic, New York, pp 47–88Google Scholar
- Fritz M, El Rawas R, Ahmad S, Klement S, Bardo MT, Kemmler G, Dechant G, Saria A, Zernig G (2010) Reversal of cocaine-conditioned place preference and mesocorticolimbic Zif268 expression by social interaction in rats. Addict Biol (in press)Google Scholar
- Green TA, Alibhai IN, Roybal N, Winstanley CA, Theobald DEH, Birnbaum SG, Graham AR, Unterberg S, Graham DL, Vialou V, Bass CE, Terwilliger EF, Bardo MT, Nestler EJ (2010) Environmental enrichment produces a behavioral phenotype mediated by low cyclic adenosine monophosphate response element binding (CREB) activity in the nucleus accumbens. Biol Psychiatry 67:28–35PubMedCrossRefGoogle Scholar
- Landau D (1986) The effects of changes and constraints on access to video game playing on alcohol consumption. Diss Abstr Int 48:1174BGoogle Scholar
- Montgomery DC, Peck A, Vining GG (2006) Introduction to linear regression analysis, 4th edn. Wiley, New YorkGoogle Scholar
- Renner MJ, Rosenzweig MR (1987) Enriched and impoverished environments: effects on brain and behavior. Springer, New YorkGoogle Scholar
- Schwendt M, Rocha A, See RE, Pacchioni AM, McGinty JF, Kalivas PW (2009) Extended methamphetamine self-administration in rats results in a selective reduction of dopamine transporter levels in the prefrontal cortex and dorsal striatum not accompanied by marked monoaminergic depletion. J Pharmacol Exp Ther 331(2):555–562PubMedCrossRefGoogle Scholar