Inhibition of hippocampoprefrontal cortex excitatory responses by the mesocortical DA system.

The prefrontal cortex (PFC) receives dopaminergic (DA) afferents from the ventral tegmental area (VTA) and excitatory inputs from the hippocampal formation. The present electrophysiological experiments performed in anaesthetized rats demonstrate that activation of the mesocortical DA system blocked the spontaneous activity of PFC neurones and the excitatory responses induced by hippocampal stimulation. These data indicate that there is a convergence in the effects of hippocampal and DA mesocortical afferents on common PFC neurones. Furthermore, a population of PFC neurones responding to hippocampal stimulation could be identified as projecting to either the nucleus accumbens and/or the VTA, suggesting that the hippocampus exerts an indirect influence on these two structures through the PFC.