Long-term light history modulates the light response kinetics of luminosity (L)-type horizontal cells in the roach retina.
We have examined the effects of prolonged periods of darkness on the responses of luminosity-type horizontal cells (L-HCs) in the freshwater cyprinid, Rutilus rutilus. Two groups of retinae were compared, those recorded after 10 min dark adaptation (SA) and those recorded after 3 h dark adaptation (LA). The results suggest that long-term light history does not modify the general responsiveness of the L-HCs in this species. However, there are apparent changes in the receptive field of the cells and modifications to the kinetics of the light-evoked response. The kinetics changes involve both a delay in the onset of light response and a selective effect on the hyperpolarizing light-ON response. Thus the mean time constant (tau) for the SA cells was 32.4+/-2.39 ms (n=62), whilst that for the LA cells was 53.4+/-3.03 ms (n=61). These effects occur in the absence of changes in the relative spectral sensitivity or threshold sensitivity of the HCs. The results suggest that in some vertebrate retinae, prolonged darkness (light-history) may regulate long-term plasticity in the kinetics of the cone-HC pathway.
Jenkins
A
A
Imperial College School of Medicine, Division of Neuroscience and Psychological Medicine, Department of Integrative and Molecular Neuroscience, Fulham Palace Road, W6 8RF, London, UK.
Hankins
M W
MW
D000818:Animals; D003530:Cyprinidae; D003623:Dark Adaptation / Q000502:physiology*; D007700:Kinetics; D008027:Light; D010775:Photic Stimulation / Q000379:methods; D010786:Photoreceptor Cells / Q000502:physiology*; D012160:Retina / Q000502:physiology; D013997:Time Factors