Time-dependent differential effects of cobalt ions on rod- and cone-driven responses in the isolated frog retina.
The effects of cobalt ions on 502-nm rod- and 575-nm cone-driven components of the b-wave of the electroretinogram were studied in the isolated frog retina. Addition of 100-150 microM cobalt initially caused a suppression of rod-driven responses and an enhancement of cone-driven responses. In the continued presence of cobalt, however, the rod-driven responses gradually recovered and the cone-driven responses became suppressed. These concentrations of cobalt had no effect on the rod- and cone-driven mass receptor potentials which were isolated in the presence of 4 mM glutamate. At higher concentrations of cobalt (1 mM or greater), both rod- and cone-driven b-wave responses were eliminated and there was no recovery in the continued presence of cobalt. The results suggest that cobalt has markedly different, time-dependent effects on signal transmission from rods and cones to second-order cells.
Dong
C J
CJ
Department of Physiology, University of Michigan, Ann Arbor 48109-0622.
McReynolds
J S
JS
Qian
H H
HH
D000818:Animals; D003035:Cobalt / Q000494:pharmacology*; D003623:Dark Adaptation; D004596:Electroretinography / Q000187:drug effects; D008027:Light; D008564:Membrane Potentials / Q000187:drug effects; D010786:Photoreceptor Cells / Q000187:drug effects*; D011894:Rana pipiens; D012160:Retina / Q000187:drug effects* / Q000502:physiology; D013569:Synapses / Q000187:drug effects; D013997:Time Factors
D003035:Cobalt