Electrical responses and K+ activity changes to light in the ocellus of the planarian Dugesia japonica.
The extracellular electrical response (ocellar potential, OP) and K+ activity changes to light were measured in the planarian ocellus by conventional and double-barreled ion-selective microelectrodes. The OP evoked by a 0.5 sec light flash is a simple monophasic potential, which is sustained during long-term illumination. The spectral sensitivity of the OP has the characteristics of a rhodopsin with lambda max 505 nm. K+ activity in the extracellular space of the ocellus in the dark was 1.1 +/- 0.2 mM (mean +/- SE, n = 6). A 0.5 sec light flash and a 120 sec long-term illumination evoked increases in the K+ activity. The maximum K+ activity change occurred at 503 nm. These results suggest that the efflux of K+ from the planarian photoreceptor into the extracellular space is caused by light, and that the OP and the increase of K+ activity are mediated by a rhodopsin.
Azuma
K
K
Department of Biology, Osaka Medical College, Japan.
Okazaki
Y
Y
Asai
K
K
Iwasaki
N
N
D000818:Animals; D004594:Electrophysiology; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology; D008839:Microelectrodes; D018408:Patch-Clamp Techniques; D010775:Photic Stimulation; D010932:Planarians / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D012243:Rhodopsin / Q000494:pharmacology
D012243:Rhodopsin; D011188:Potassium