Suppression of retinal spike discharge by dipropylacetate (Depakene): a possible involvement of GABA

Effects of dipropylacetate (DPA) were studied on spike discharges in the isolated carp retina. (1) DPA, applied electrophoretically or by pressure-microinjection in the vicinity of the recording electrode at the inner plexiform layer, consistently activated spike discharges. (2) DPA introduced into the perfusate produced complex actions; some units responded to DPA with an initial activation followed by suppression of spike discharges. (3) When gamma-aminobutyric acid (GABA) was applied electrophoretically together with perfusion of DPA, the depressing effect was greater than that obtained with each of these compounds alone. Bicuculline in the perfusate markedly attenuated the depressing actions of GABA or DPA singly, or in combination. (4) It is concluded that the delayed suppression of spike discharges by perfused DPA appears to be mediated by GABA-receptors on ganglion cells in the carp retina.