An electrophysiological test of the effect of the temporal pattern of light adaptation on teleost H1 type horizontal cell plasticity.
The possible importance of the temporal pattern of photon delivery in light adaptation-induced physiological plasticity in the outer retina of carp was tested by intracellular recording. Steady and flicker (3 Hz) background adaptation was applied whilst recording chromatic voltage responses of H1 type horizontal cells (HCs) to 680 and 440 nm full-field test flashes (generating response amplitudes of V(r) and V(b), respectively). A third parameter V(b)/V(r) (B/R) was calculated as an indicator of the cells' short/long wavelength relative spectral contrast. Steady light adaptation increased V(r) and to a lesser extent V(b), and reduced B/R. Flicker adaptation also increased V(r) (by a similar amount), but, unlike steady adaptation, consistently decreased V(b). The reduction in B/R was statistically greater for flicker than for steady adaptation, although the former delivered half as many photons to the retina. These results suggest that the temporal pattern of light adaptation is indeed an important determinant of qualitative and quantitative aspects of plasticity induced in the outer retina, and complement earlier morphological findings. The effects are discussed in terms of dopamine and nitric oxide as underlying possible neurochemical control mechanisms.
Haamedi
S N
SN
Neurobiology Group, Department of Biology, Imperial College of Science, Technology and Medicine, Sir Alexander Fleming Building, SW7 2AZ, London, UK.
Djamgoz
M B
MB
D000221:Adaptation, Ocular / Q000502:physiology*; D000818:Animals; D002347:Carps / Q000502:physiology*; D004298:Dopamine / Q000378:metabolism; D005425:Flicker Fusion / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism; D010775:Photic Stimulation; D012160:Retina / Q000502:physiology*
D009569:Nitric Oxide; D004298:Dopamine