Dendritic morphology and retinal distribution of tyrosine hydroxylase-like immunoreactive amacrine cells in Bufo marinus.

Tyrosine hydroxylase-like immunoreactive (TH-IR) amacrine cells (ACs) in the retina of metamorphosing and adult Bufo marinus were visualized, and their retinal distribution established, using immunohistochemistry on retinal wholemount and sectioned material. The somata of TH-IR ACs were located in the innermost part of the inner nuclear layer (INL). Their dendrites branched predominantly in the scleral sublamina of the inner plexiform layer (IPL), with sparse branching also in the vitreal sublamina. In the retinae of metamorphosing animals 592 +/- 113 (mean +/- S.D.) immunoreactive cells and in adult 5,670 +/- 528 cells were found. Usually 1, 2 or 3 stem dendrites arose from the somata of TH-IR cells which branched 2 or 3 times. In the adult retinae the dendritic field sizes of immunoreactive cells were in the range of 0.059 +/- 0.012 mm2, which resulted in a considerable dendritic overlap across the retina. TH-IR cells were unevenly distributed over the retina, with 72 cells/mm2 in the central temporal retina, 45-50 cells/mm2 along the naso-temporal axis of the retina and 25 cells/mm2 in the dorsal and ventral peripheral retina. The average density was 36 +/- 6 cells/mm2. A considerable number of TH-IR cells (range 52-133, n = 4) were displaced into the ganglion cell layer (GCL) of the retina. The mean soma sizes of immunoreactive cells were significantly higher in the low density (95 +/- 13 microns 2) than in the high cell density areas (86 +/- 12 microns 2).(ABSTRACT TRUNCATED AT 250 WORDS)