Age-dependent differences in the strength and persistence of psychostimulant-induced conditioned activity in rats: effects of a single environment-cocaine pairing

• Published in: Behavioural pharmacology Vol. 25; no. 7; p. 695
• Main Authors: McDougall, Sanders A, Pipkin, Joseph A, Der-Ghazarian, Taleen, Cortez, Anthony M, Gutierrez, Arnold, Lee, Ryan J, Carbajal, Sandra, Mohd-Yusof, Alena
• Format: Journal Article
• Language: English
• Published: England 01.10.2014
• Subjects: Age Factors; Animals; Behavior, Animal - drug effects; Central Nervous System Stimulants - administration & dosage; Central Nervous System Stimulants - pharmacology; Cocaine - administration & dosage; Cocaine - pharmacology; Conditioning, Classical - drug effects; Environment; Habituation, Psychophysiologic; Male; Rats; Rats, Sprague-Dawley; Time Factors
• ISSN: 1473-5849
• DOI: 10.1097/FBP.0000000000000085

The aim of the present study was to determine the strength and persistence of cocaine-induced conditioned activity in young and adult rats. A one-trial protocol has proven useful for studying the ontogeny of psychostimulant-induced behavioral sensitization; therefore, a similar procedure was used to examine conditioned activity. On postnatal day (PD) 19 or PD 80, rats were injected with saline or cocaine in either a novel test chamber or the home cage. After various drug abstinence intervals (1-21 days), rats were injected with saline and returned to the test chamber, where conditioned activity was assessed. In a separate experiment, we examined whether cocaine-induced conditioned activity was a consequence of Pavlovian conditioning or a failure to habituate to the test environment. The results indicated that adult rats showed strong one-trial conditioned activity that persisted for at least 21 days, whereas young rats did not show a conditioned locomotor response. The conditioned activity shown by adult rats did not result from a failure to habituate to the cocaine-paired environment. These results indicate that cocaine-paired contextual stimuli differentially affect behavior depending on the age of the animal. The data obtained from adult rats have potential translational relevance for humans because a single environment-drug pairing caused long-term alterations in behavior.