| Abstract: | Synaptic transmission between photoreceptors and horizontal cells in the turtle retina blocked by Co2+ ions can be restored by passing constant radial current through the retina which depolarizes presynaptic receptor terminals. This finding is unassociated with current action on horizontal cells themselves, since polarization of these cells via an intracellular microelectrode did not restore response to light. The unblocking effect of depolarization at the receptor synaptic endings consists of two components: the opening of additional calcium channels not blocked by Co2+ at the presynaptic membrane and cobalt-induced voltage-dependent blockade of clacium channels. The latter may explain the paradoxical phenomenon of increased response to the action of moderate light in horizontal cells during cobalt-induced partial blockade of synaptic transmission.Institute for Research into Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 20, No. 3, pp. 374–383, May–June, 1988. |
