Decline of blocking effect of cobalt ions on transmission from photoreceptors to horizontal cells during its prolonged application.
In high-Mg2+ medium, luminosity-type cone horizontal cells (L-cells) hyperpolarized and lost their photoresponses at a full membrane hyperpolarization of about -80 mV. These effects of high-Mg2+ are attributed to the blockade of transmitter release from photoreceptors. Application of Co2+ hyperpolarized the L-cells at first and the photoresponses disappeared at full membrane hyperpolarization. After a little while, however, the membrane potential began to depolarize and the light stimuli again evoked responses. The recovery of the membrane potential and photoresponses indicates that prolonged application of Co2+ weakens its ability to block transmission from photoreceptors to L-cells.
Umino
O
O
Department of Physiology, Tokyo Women's Medical College, Japan.
Watanabe
K
K
D000818:Animals; D002347:Carps / Q000502:physiology; D003035:Cobalt / Q000494:pharmacology*; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology*; D010786:Photoreceptor Cells / Q000502:physiology*; D012160:Retina / Q000166:cytology*; D009435:Synaptic Transmission / Q000187:drug effects*
D003035:Cobalt; D008274:Magnesium