SCHOLL, A.M.*; VAJDA, A.M.; NORRIS, D.O.; Univ. of Colorado, Boulder; Univ. of Colorado, Boulder; Univ. of Colorado, Boulder: Androgen Increases Tyrosine Hydroxylase Immunoreactivity in the Preoptic Neurons of the Brain of Developing Tiger Salamander, Ambystoma tigrinum

This study investigated possible effects of precocious exposure to the gonadal steroids estradiol (E₂) and dihydrotestosterone (DHT) on the expression of immunoreactive tyrosine hydroxylase (TH-ir) neurons of the anterior preoptic area (aPOA) and the posterior tuberculum (TP) of sexually undifferentiated, larval tiger salamanders (Ambystoma tigrinum). Larvae were injected intraperitoneally every three days for thirty days with 15 microgram E₂ or 15 microgram DHT suspended in saline or vehicle alone. At the end of the treatment period, animals were killed by rapid decapitation and brains were fixed in Bouin�s prior to standard preparations for immunohistochemistry. DHT, but not E₂, stimulated TH-ir cell numbers in the aPOA. Neither E₂ nor DHT affected TH-ir cell number in the TP. These results assist in the development of a neuroendocrine model for the exogenous effects of gonadal steroid hormones and the chemicals that mimic the gonadal steroid hormones (endocrine-disrupting chemicals). This research was supported by a Howard Hughes grant awarded by the Undergraduate Research Opportunities Program (UROP) at the University of Colorado at Boulder to AMS and by a grant from the department of Environmental, Population, and Organismic Biology at the University of Colorado at Boulder, Rozella Smith Fund, to AMV.