(RS)-AMPA (10-3-10-4 M) causes depolarizations of cultured rat spinal and brainstem neurones. The depolarization by (RS)-AMPA is clearly dose-dependent, although there is a great variability of effects between individual neurones. Application of (RS)-AMPA at 10-5 M produces only small depolarizations (3-7 mV), whereas at 10-4 M, the amplitudes of the depolarizations ranged from 4 to 33 mV. (RS)-AMPA also causes an increase of the discharge rate of spontaneously firing neurones or sometimes evoked a short burst of action potentials in silent cells. (RS)-AMPA exerts its depolarizing effects by activating glutamate/quisqualate receptors without affecting NMDA receptors.