The action of substance P on mesencephalic reticular and substantia nigral neurones of the rat.

Extracellular recordings were made from neurones in the mesencephalic reticular formation and substantianigra of the rat which was anaesthetized with urethane 1.5-2 g/kg i.p. Out of 44 cells tested 42 were excited by Substance P applied iontophoretically and in some cases this excitation was rapid. Evidence is presented for Substance P as a putative excitatory transmitter onto reticular and nigral neurones possibly released from primary sensory afferents.