IMPAIRED RETINAL FUNCTION IN YOUNG LABRADOR RETRIEVER DOGS HETEROZYGOUS FOR LATE-ONSET ROD-CONE DEGENERATION

Xenon-flash d.c.-electroretinograms were recorded from dark adapted, r od-cone degenerate homozygote affected (n = 6), heterozygote carrier ( n = 3) and control retinas (n = 4) at 3 and 4 months of age, starting at 0.6 log units below control PII threshold. One log unit higher stim uli were necessary to evoke PII in heterozygote and affected retinas c ompared to controls, Unique to the heterozygotes, double peaked PII re sponses that were evoked by -2 log relative units intensity stimulatio n were significantly (P = 0.028) lower in amplitude than those of cont rols, PII amplitudes of homozygotes were significantly (P = 0.005) low er in amplitude than those of controls at both ages examined in respon se to -2 and 0 log relative intensity stimulation, No differences were found in scotopic threshold response amplitudes or times to peak betw een the three groups. Homozygote affected PII times to peak were signi ficantly (P = 0.005) shorter in relation to controls at -2 log units, Findings suggest that heterozygotes exhibit an impaired retinal functi on which can be demonstrated at 3 and 4 months in this mutant. Copyrig ht (C) 1996 Elsevier Science Ltd