Differential effects of intra-accumbens and systemic amphetamine on latent inhibition using an on-baseline, within-subject conditioned suppression paradigm.
Latent inhibition (LI) is a phenomenon in which repeated, non-reinforced presentation of a stimulus retards subsequent conditioning to that stimulus. Several recent experiments have suggested that LI is abolished following acute, low doses of amphetamine given during pre-exposure and conditioning, and this effect has been attributed to amphetamine-induced changes in dopamine levels in the nucleus accumbens. Experiments 1 and 2 examined the effects of two doses of intra-accumbens d-amphetamine (10 micrograms/microliters and 3 micrograms/microliters) on LI in an on-baseline, within-subject conditioned suppression paradigm. There was no effect of either dose on LI, but a significant disinhibition of conditioned suppression resulted in a retardation of learning. In experiment 3 the effects of a low dose of systemic d-amphetamine (0.5 mg/kg) on latent inhibition were examined. The results replicated the abolition of LI found in previous studies, and demonstrated enhanced post-shock suppression in amphetamine-treated animals. These data provide no evidence for the involvement of the mesolimbic dopamine system in LI.
Killcross
A S
AS
Department of Experimental Psychology, University of Cambridge, UK.
Robbins
T W
TW
D000161:Acoustic Stimulation; D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects*; D003913:Dextroamphetamine / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005108:Extinction, Psychological / Q000187:drug effects; D007267:Injections; D008297:Male; D009714:Nucleus Accumbens / Q000033:anatomy & histology / Q000502:physiology*; D051381:Rats
D003913:Dextroamphetamine