Immunocytochemical and Biochemical Evidence for Aromatase in Neurons of the Retina, Optic Tectum and Retinotectal Pathways in Goldfish

Using an animal model in which neural aromatase is apparently overexpressed (the goldfish, Carassius auratus) and an antihuman placental antibody which specifically crossreacts with goldfish brain aromatase, aromatase-immunoreactive neuronal cell bodies and fibers have been localized within the retina. These include a subset of horizontal cells, bipolar cells, and amacrine cells of the inner nuclear layer, some fibers of the outer and inner synaptic layers and certain cells of the ganglion cell layer; photoreceptors were never labeled. Some ganglion cell projections to the brain via the optic nerve and optic tract were aromatase-positive, as were small neurons of the stratum periventriculare (SPV) and fibers of two other strata of the optic tectum. Aromatase activity, as measured by ³H]estrogen formation from ³H]androgen by tissue homogenates and cell cultures, confirmed the presence of aromatase in retina and in brain regions containing the optic tectum. This localization of the rate-limiting enzyme in estrogen biosynthesis suggests that neuroestrogen derived from circulating androgen may modulate transmission and integration of visual information important for reproduction in this species.