Abstract
The anterior cingulate cortex (AC) component of the medial prefrontal cortex (mPFC) has been implicated in attention and working memory as measured by trace conditioning. Since dopamine (DA) is a key modulator of mPFC function, the present study evaluated the role of DA receptor agents in rat AC, using trace fear conditioning. A conditioned stimulus (CS, noise) was followed by an unconditioned stimulus (US, shock) with or without a 10s trace interval interposed between these events in a between-subjects design. Conditioned suppression of drinking was assessed in response to presentation of the CS or an experimental background stimulus (flashing lights, previously presented for the duration of the conditioning session). The selective D1 agonist SKF81297 (0.05μg/side) or D1 antagonist SCH23390 (0.5μg/side) was administered by intra-cerebral microinfusion directly into AC. It was predicted that either of these manipulations should be sufficient to impair trace (but not delay) conditioning. Counter to expectation, there was no effect of DA D1 modulation on trace conditioning as measured by suppression to the noise CS. However, rats infused with SKF81297 acquired stronger conditioned suppression to the experimental background stimulus than those infused with SCH23390 or saline. Thus, the DA D1 agonist SKF81297 increased conditioned suppression to the contextual background light stimulus but was otherwise without effect on fear conditioning.
Highlights
There is good evidence that the medial prefrontal cortex is essential for the smooth running of a number of cognitive functions including selective and divided attention, short term working memory and behavioral flexibility (Arnsten, 2000; Granon and Poucet, 2000; Kolb, 1984)
We have recently reported evidence for DA D1 modulation of trace conditioning and this effect was mediated in medial prefrontal cortex (mPFC), whilst we compared the effects of DA D1 agonist in prelimbic and infralimbic sub-regions (Pezze et al, 2015), the role of the anterior cingulate cortex (AC) was not examined in this previous study
The present experiment evaluated the effect of DA D1 receptor modulation on cognitive function in the AC as assessed by trace conditioning measured in a conditioned emotional response (CER) procedure in which the level of contextual conditioning is routinely assessed
Summary
There is good evidence that the medial prefrontal cortex (mPFC) is essential for the smooth running of a number of cognitive functions including selective and divided attention, short term working memory and behavioral flexibility (Arnsten, 2000; Granon and Poucet, 2000; Kolb, 1984). The catecholaminergic toxin 6-hydroxydopamine injected within mPFC impaired performance in spatial delayed alternation tasks in both rats (Simon, 1981) and primates (Brozoski et al, 1979). This behavioral deficit was reversed by the administration of the DA precursor L-DOPA or the DA agonist apomorphine (Brozoski et al, 1979). These early results suggested that DA is a key modulator of mPFC function. Subsequent research has upheld the hypothesis that mPFC DA modulates attention and memory functions
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