ISSN:
1432-0878
Keywords:
Synapse
;
Feedback
;
Plasticity
;
Colour vision
;
Photoreceptors
;
Horizontal cells
;
Rutilus rutilus (Teleostei)
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary A negative feedback interaction between luminosity type horizonatal cells (HCs) and green-sensitive cones generates the long-wavelength-sensitive depolarizing response in biphasic chromaticity type HCs. This interaction is suppressed in the dark and is potentiated by light adaptation of the retina. HCs are morphologically ‘plastic’; during light adaptation, their dendritic terminals within cone pedicles extend, giving rise to “spinules”. This paper examines whether there is a quantitative correlation between the time course of light-dependent formation of the spinules and enhancement of the feedback interaction. The strength of the feedback interaction in isolated retinac of the roach was determined as the ‘neutral wavelength’ at which reversal of spectral response polarity occurred in biphasic HCs. A good correlation was found between the ‘neutral wavelength’ and the spinule/ribbon ratios of retinae. Biphasic HCs were intracellularly stained with horseradish peroxidase and the correlative ultrastructure of the contacted pedicles was examined. ‘Neutral wavelength’ was found to be correlated with the spinule number, weighted according to the number of synaptic contacts mediating feed-forward transmission. The latter was estimated from the total number of labelled Cb/H2 HC processes (central and lateral) at synaptic triads. A model in which spinules mediate the negative feedback interaction of HCs in the retina of cyprinid fish is presented.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00297497
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