Noradrenaline-octopamine interactions on cortical neurones in the rat.

The interactions of noradrenaline and octopamine were tested on spontaneously active neurones in the rat cerebral cortex. When applied with weak iontophoretic currents such that no change in baseline firing rate occurred, octopamine profoundly enhanced both depressant and excitatory responses to noradrenaline. Similar applications of octopamine did not alter depressant responses to dopamine or depressant or excitatory responses to iontophoretically applied 5-hydroxytryptamine. The results could support a role of octopamine as a co-transmitter or modulator of noradrenaline mediated neurotransmission.