Methylphenidate significantly alters the functional coupling between the prefrontal cortex and dopamine neurons in the ventral tegmental area

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Abstract

Amphetamine-like psychostimulants, including methylphenidate, have been shown to produce two opposing effects on dopamine (DA) neurons: a DA receptor-mediated feedback inhibition and a non-DA receptor-mediated excitation. To test whether the latter effect is mediated through the prefrontal cortex (PFC), we made dual-site recordings from the PFC and ventral tegmental area (VTA). Consistent with previous reports, methylphenidate inhibited VTA DA neurons. The D2 receptor antagonist raclopride completely reversed the inhibition and further increased the activity, particularly bursting, to above pre-drug baseline. This increase in DA cell activity was blocked by the α1 receptor antagonist prazosin, suggesting an effect mediated through α1 receptors. Recordings in the PFC showed that methylphenidate increased PFC UP state duration and shifted the functional coupling between the PFC and DA neurons from negative to positive. The former effect was partially reversed by not only prazosin, but also raclopride, whereas the latter was reversed only by raclopride. These results suggest that methylphenidate increases PFC cell activity through both α1 and D2 receptors. Its effect on PFC-DA cell functional coupling, however, is mediated through D2 receptors. The finding that the latter effect was unaffected by prazosin further suggests that it does not play a significant role in the α1-mediated excitatory effect of methylphenidate on DA neurons. However, the shift in PFC-DA cell functional coupling from negative to positive may significantly alter the relative timing between DA and glutamate release from DA and PFC terminals and thus the synaptic plasticity that depends on DA-glutamate interaction.

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