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Blockade of D‐1 dopamine receptors in the medial prefrontal cortex produces delayed effects on pre‐ and postsynaptic indices of dopamine function in the nucleus accumbens

The present experiments assessed the acute and delayed effects of D‐1 dopamine (DA) receptor blockade in the medial prefrontal cortex (mPFC) on pre‐ and postsynaptic indices of DA neurotransmission in the nucleus accumbens (N.Acc). Different groups of rats received intra‐mPFC injections of saline (control animals) or the D‐1 DA receptor antagonist SCH‐23390 (0.25 μg/side). Acutely, intra‐mPFC injections of this antagonist did not affect spontaneous locomotion but significantly increased the locomotion induced by intra‐N.Acc. amphetamine (1.5 μg /side), in agreement with our earlier findings [Vezina et al. (1991) Eur. J. Neurosci., 3:1001‐1007]. When tested two days post‐injection, however, mPFC‐SCH‐23390 preexposed animals showed lower levels of locomotor activity than Control animals in response to intra‐N.Acc. injections of amphetamine. This effect was not observed in other animals preexposed two days earlier to mPFC injections of amphetamine (2.5 tg/side) or the D‐2 DA receptor antagonist sulpiride (1.0 μg/side). Animals preexposed two days earlier to mPFC SCH‐23390 also showed higher levels of locomotor activity (+ 98%) when tested with intra‐N.Acc. injections of the D‐1 DA receptor agonist SKF‐38393 (1.0 μg/side) and a 36% increase in maximal DAsensitive adenylate cyclase activity in comparison to Control animals. These effects were no longer observed in animals tested seven days following the mPFC SCH‐23390 injections. These results demonstrate delayed actions resulting from cortical D‐1 DA receptor blockade. They suggest, in a way consistent with previous findings [Herve et al. (1989) J. Neurosci., 9:3699‐3708] that mPFC D‐1 DA receptors are involved in the presynaptic regulation of DA neuron reactivity as well as the postsynaptic regulation of D‐1 DA receptors in subcortical DA terminal and receptor fields such as the N.Acc. © 1994 Wiley‐Lies, Inc.