The Journal of Neuroscience, June 15, 1998, 18(12):4775-4784
Circadian Rhythms of Rod-Cone Dominance in the Japanese
Quail Retina
Mary K.
Manglapus1,
Hiroyuki
Uchiyama2,
Neal F.
Buelow1, and
Robert B.
Barlow1
1 Center for Vision Research, State University of New
York Health Science Center, Syracuse, New York 13210, and
2 Department of Information and Computer Science, Faculty
of Engineering, Kagoshima University, Kagoshima 890, Japan
When the Japanese quail is held in constant darkness, retinal
responses (ERG b-waves) increase during the animal's subjective night
and decrease during its subjective day. Rod photoreceptors dominate the
b-wave responses (
max = 506 nm) to all stimulus intensities at night but only to those intensities below the cone threshold during the day. Above the cone threshold, cones dominate b-wave responses (max, ~550-600 nm) during the
day regardless of the state of retinal adaptation. Apparently a
circadian oscillator enables cone signals to block rod signals during
the day but not at night. The ERG b-wave reflects the activity of
bipolar cells that are postsynaptic to rods and cones. The ERG a-wave
reflects the activity of both rods and cones. The amplitude of the
isolated a-wave (PIII) changes with time of day, as does that of the
b-wave, but its spectral sensitivity does not. The PIII responses are maximal at ~520 nm both day and night and may reflect multiple receptor mechanisms. The shift in rod-cone dominance detected with the
ERG b-wave resembles the Purkinje shift of human vision but, unlike the
Purkinje shift, does not require a change in ambient light intensity.
The shift occurs in constant darkness, with a period of ~24 hr
indicative of a circadian rhythm in the functional organization of the
retina.
Key words:
circadian rhythm; retina; ERG; quail; rod-cone
dominance; photoreceptor
Copyright © 1998 Society for Neuroscience 0270-6474/98/18124775-10$05.00/0
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