Altered development of dopaminergic cells in the retina of Weaver mice

Postnatal degeneration of dopaminergic (DA) cells is known to occur in mese ncephalic nuclei of mutant weaver mice, whereas retinal DA content is repor ted to be unchanged in the adult animal. To determine whether morphological changes occur in the weaver retinal DA system, we compared weaver and cont rol developing and adult retinas after tyrosine hydroxylase (TH) immunohist ochemistry. The density and distribution of DA cells were analyzed using Di richlet tessellation. Not only was no DA cell loss found in adult weaver re tinas, but we even observed an increase in DA cells in weaver compared to c ontrol retinas between postnatal days 14 and 30. Furthermore, some unusual features were found during the latter period: atypical cells (representing a maximum of 12% of the whole DA cell population) were observed, and these differed from typical DA cells in terms of both location (slightly more ext ernal within the inner nuclear layer) and appearance (flat somata, round an d clear nuclei, thick dendritic trunks emerging laterally and giving rise t o horizontal processes). Some of the atypical cells were intermingled in a delicate network lying in a more outer focal plane than the main DA plexus. The expression of GIRK2, a G protein-related inward rectifying K+ channel responsible for the weaver syndrome, was investigated. Although no GIRK2 la beling was demonstrated in DA cells, its possible involvement in the transi ent disturbances observed in the weaver DA retinal system is discussed. J. Comp. Neurol. 412:656-668, 1999. (C) 1999 Wiley-Liss, Inc.