title: The acquisition, extinction and spontaneous recovery of Pavlovian drug conditioning induced by post-trial dopaminergic stimulation/inhibition.
abstract: In contextual drug conditioning, the onset of the drug treatment is contiguous with the contextual cues. Evidence suggests that drug conditioning also can occur if there is a discontinuity between the onset of the drug effect and offset of the contextual cues. Here we examine whether post-trial contextual drug conditioning conforms to several Pavlovian conditioning tenets namely: acquisition, extinction and spontaneous recovery. Six groups of rats received apomorphine (0.05 or 2.0mg/kg) and vehicle immediately or after a 15min delay following a 5min non-drug exposure to an open-field during three successive days (conditioning phase). The extinction phase occurred on days 4-8, in which all post-trial treatments were vehicle injections. After 2days of non-testing, the final test was performed. The results showed that on the first test day, the activity levels of the 6 groups were statistically equivalent. On test day 2, there were marked differences in activity levels selectively between the two immediate post-trial apomorphine treatment groups. The immediate low dose apomorphine group displayed a reduction in activity and the immediate high dose group an increase in activity relative to their day 1 levels. The activity levels of both vehicle groups and both apomorphine delay groups remained equivalent to their day 1 activity levels. On test day 3, the differences in activity levels between the two immediate post-trial apomorphine groups increased but the activity levels of the vehicle groups and the 15min delay post-trial apomorphine groups remained unchanged. In the extinction phase, the conditioned activity differences between the two immediate post-trial apomorphine groups were gradually eliminated. During the final test, the activity differences between the immediate post-trial apomorphine groups were partially restored, indicative of spontaneous recovery. These findings are consistent with several basic elements of Pavlovian conditioning and are supportive of drug induced trace conditioning.
authors.affiliation: Behavioral Pharmacology Group, Laboratory of Morphology and Pathology Animal Health, State University of North Fluminense Darcy Ribeiro, Avenida Alberto Lamego, 2000, Campos dos Goytacazes 28013-600, RJ, Brazil.
authors.forename: Breno Garone
authors.initials: BG
authors.lastname: Santos
authors.affiliation: Research and Development (151), VA Medical Center and SUNY Upstate Medical University, 800 Irving Avenue, Syracuse, NY 13210, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Carey
authors.affiliation: Behavioral Pharmacology Group, Laboratory of Morphology and Pathology Animal Health, State University of North Fluminense Darcy Ribeiro, Avenida Alberto Lamego, 2000, Campos dos Goytacazes 28013-600, RJ, Brazil. Electronic address: marinete@uenf.br.
authors.forename: Marinete Pinheiro
authors.initials: MP
authors.lastname: Carrera
mesh_terms: D000818:Animals; D001058:Apomorphine / Q000494:pharmacology*; D003214:Conditioning, Classical / Q000187:drug effects*; D004298:Dopamine / Q000494:pharmacology*; D008297:Male; D051381:Rats; D017208:Rats, Wistar
chemical_list: D001058:Apomorphine; D004298:Dopamine
keywords: Apomorphine; Extinction; Novel environment; Post-trial; Spontaneous recovery; Trace-conditioning