Excitatory nature of dopamine in the nigro-caudate pathway

Inputs from the substantia nigra (SN) to the caudate nucleus (Cd) and the effects of electrophoretic dopamine on Cd neurones were studied in cats anaesthetized with pentobarbitone with intracellular techniques. Single shock electrical stimulation of the SN or the medial forebrain bundle (MFB) induced monosynaptic EPSPs in Cd neurones. Dopamine depolarized Cd neurones and chlorpromazine suppressed the SN or MFB induced EPSPs. Appropriate controls indicate that the drug effects were not artifactual. Some recorded neurones were identified by procion yellow dye injection as the medium-size intrinsic Cd neurones.