P 426 The weaver mutation: Effect on the dopamine system of the retina

&sJ&+BI to demonstrate the “ccurence of en oscillator using dopemine (DA) end q elatonin :MEL). that regulates the daily rhythm Of light/dark adaptetiorl in the ret retina, es exists in “on mammalian species. &&&&: Biochemical assays fo:: DA, di-hydroryphenylacetic acid (DOPACI. homovanilic acid (HVAj. N-acetyl-serotonin, and MEL by HPLC with emperometric detecticm. and immunocytochemistry of DA receptors in Wistar end Brow” Norway (BN) adult male ret8 submitted foe 10 days to different lighting cycles (LL-lightadapted, DD-dark-adapted, DL-12/U cycle), or blockade of DA synthesis by alpha-methyl-paratyrosine (alpha-mpt). or blockade Of DA-receptors by clozapine. w: A D&like receptor wee localized on photoreceptor inner segments with both en anti-D2 antiserum (directed against the 3rd intracytoplasmic loop) end a” anti-idiotypic antibody. in DL rets. The expression of this receptor ves enhanced in DD tat* followi”g -dark-induced DA deprivation. MEL ves quantifiable in DL BN rats sacrificed et night, while only N&etyl-serotoni” wee detectable in Wistar rats. The retinal DA content was Rreatly decreased (80%) after blockade of tyrosine hydrorylase activity by alpha-mpt. In this condition. MEL was enhanced (about 40X) in DL BN rats. The MEL content also incressed (about 30X) following blockade of the DP-like receptor by clozwine. in DL BN rats sacrificed et night. &&&&J&: The -results confirm the implication of-DA in the regulstion of MEL synthesis by photoreceptor cells through e D&like receptor I” rats. The <:lorapi”e-induced increase in MEL synthesis indicates that the receptor involved is likely to be of the D4 subtype. THE WEAVER MUTATION: EFFECT ON THE DOPAMINE SYSTEM OF THE RETINA.