Neuron responses to substance P and enkephalin in rat dorso-lateral septum in vitro

Using an in vitro brain slice technique the responses of spontaneously active neurons in the rat dorso-lateral septum to 10 nM substance P (SP) and enkephalin were determined. Fewer neurons responded to SP (41%) than to enkephalin (55%). The SP responses were 13 excitations, 14 inhibitions, the enkephalin responses were 13 excitations, 14 inhibitions and 11 responded to both, 6 of these were inhibited by both. Immunocytochemical techniques have shown there is a discrete localisation of SP and enkephalin axons and terminals in the rat septum. SP responsive neurons were associated with the SP terminal-rich region (p = 0.01) but no association was found for enkephalin responses in the enkephalin terminal-rich region (p = 0.7).