THE GOLDFISH AS A MODEL FOR STUDYING NEUROESTROGEN SYNTHESIS, LOCALIZATION, AND ACTION IN THE BRAIN AND VISUAL-SYSTEM

Organizational and activational effects of estrogen (E) in the central nervous system (CNS) are exerted directly by circulating E and indire ctly after aromatization of circulating androgen to E in the brain its elf. Understanding an environmental chemical's ability to disrupt E-de pendent neural processes, therefore, requires attention to both pathwa ys. Because aromatase (Aro) is highly expressed in teleost brain, when compared to mammals and other vertebrates, fish are technically advan tageous for localization and regulation studies and may also provide a model in which the functional consequences of brain-derived (neuro-)E synthesis are exaggerated. Recently, Aro was immunolocalized in cell bodies and fiber projections of second- and third-order neurons of the goldfish retina and in central visual processing areas. Authentic Aro enzyme activity was verified biochemically, suggesting a heretofore u nrecognized role of sex steroids in the visual system. Initial studies show that in vivo treatment with aromatizable androgen or E increases calmodulin synthesis and calmodulin protein in retina and also affect s retinal protein and DNA. Whether there are related changes in the pr ocessing of visual information that is essential for seasonal reproduc tion or in the generative and regenerative capacity of the goldfish vi sual system requires further investigation.