External sodium ions are required for the light response in pineal photoreceptors.
Photoreceptor cells of the pineal organ of river lamprey, Lampetra japonica, showed hyperpolarizing light responses associated with a decrease in membrane resistance. Effects of external ion concentrations (Na+, K+, Li+, Cl-) on the light response and the resting membrane potentials were investigated. The average resting membrane potential in the standard solution was -29.7 +/- 7.3 mV (mean +/- SD, n = 125) and the amplitude of the response to white light (1 sec, 1.4 X 10(-8) W/cm2) was -20.4 +/- 6.3 mV (n = 125). The amplitude depended largely on external Na+ concentration. The change was 18 mV/10-fold increase of Na+ concentration, and the external Na+ was essential for generation of the response.
Samejima
M
M
1st Department of Physiology, Hamamatsu University School of Medicine, Japan.
Morita
Y
Y
D000818:Animals; D002712:Chlorides / Q000494:pharmacology; D002794:Choline / Q000494:pharmacology; D005399:Fishes / Q000502:physiology*; D007798:Lampreys / Q000502:physiology*; D008027:Light; D008094:Lithium / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D010786:Photoreceptor Cells / Q000187:drug effects / Q000502:physiology*; D010870:Pineal Gland / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology*
D002712:Chlorides; D008094:Lithium; D012964:Sodium; D002794:Choline; D011188:Potassium