ORIGINAL INVESTIGATION Dopaminergic modulation of appetitive trace conditioning: the role of D1 receptors in medial prefrontal cortex

# The Author(s) 2015. This article is published with open access at Springerlink.com Rationale Trace conditioning may provide a behavioural model suitable to examine the maintenance of ‘on line ’ infor-mation and its underlying neural substrates. Objectives Experiment la was run to establish trace condition-ing in a shortened procedure which would be suitable to test the effects of dopamine (DA) D1 receptor agents administered by microinjection directly into the brain. Experiment lb exam-ined the effects of the DA D1 agonist SKF81297 and the DA D1 antagonist SCH23390 following systemic administration in pre-trained animals. Experiment 2 went on to test the effects of systemically administered SKF81297 on the acquisition of trace conditioning. In experiment 3, SKF81297 was adminis-tered directly in prelimbic (PL) and infralimbic (IL) sub-regions of medial prefrontal cortex (mPFC) to compare the role of different mPFC sub-regions. Results Whilst treatment with SCH23390 impaired motor responding and/or motivation, SKF81297 had relatively little effect in the pre-trained animals tested in experiment 1b. How-ever, systemic SKF81297 depressed the acquisition function at the 2-s trace interval in experiment 2. Similarly, in experi-ment 3, SKF81297 (0.1 μg in 1.0 μl) microinjected into either PL or IL mPFC impaired appetitive conditioning at the 2-s trace interval. Conclusions Impaired t race condi t ioning under SKF81297 is likely to be mediated in part (but not exclusively) within the IL and PL mPFC sub-regions. The finding that trace conditioning was impaired rather than enhanced under SKF81297 provides further evi-dence for the inverse U-function which has been sug-gested to be characteristic of mPFC DA function