[The presence of an albino ERG in the pigmented rat: genetic implications (author's transl)].

UNLABELLED: The electroretinogram (ERG) of the albino rat (genotype c/c) differs from that of the pigmented rat (hooded, Long-Evans) by the attenuation of the b-wave and the disappearance of the c-wave which is replaced by a negative component. The present study has shown that a similar alteration in the ERG is present in the hypodactyl hooded rat (genotype hd/hd) (Fig. 1). The comparative analysis of the recordings indicated that: 1. The detection thresholds for the a and b waves were identical in the three varieties (Fig. 2). 2. The wave-form of the P III component observed after ischemia was also identical in the three strains (Fig. 1). 3. The modifications in the ERG induced by sodium azide (Fig. 4) and sodium iodate (Fig. 5) in the hd/hd rat are the same as those which have been reported in the c/c strain, and (as in the latter case) the absence of the c-wave is not due to the disappearance of P I, but rather to an attenuation of this component resulting in a negative algebraic sums of P I and P III (Fig. 6). 4.

IN CONCLUSION: the alterations in the ERG recording, observed in albinos, were interpreted as being due to some fragility in the photoreceptors, consequent to a lack of pigmentary protection. Such an interpretation is invalidated by the fact that a similar ERG pattern was found in both pigmented and albino rats. Because genetic deficiencies other that the absence of a chromogene factor can modify the ERG, it is suggested that the c-gene, as is the case for the hd-gene, could be responsible for a disturbance of foetal erythropoiesis. Thus, the resulting circulatory problems, without provoking any visible structural effects, would nevertheless affect retinal functioning.