Differential sensitivity of presumed dopaminergic and non-dopaminergic neurones in rat substantia nigra to electrophoretically applied substance P.

Substance P (SP) was administered by microelectrophoresis to physiologically identified substantia nigra neurones in halothane anaesthetized rats. Dopaminergic neurones of the substantia nigra compacta (SNC) were markedly less sensitive to SP than non-dopaminergic cells of the substantia nigra reticulata (SNR) when the peptide was administered with the same micropipettes. Identified substantia nigra neurones were also differentially sensitive to other putative transmitters including dopamine, 5-HT and acetylcholine. No interactions could be demonstrated between SP and the responses to other transmitters.