Identification of androgen metabolic pathways in the brain of little brown bats (Myotis lucifugus): sex and seasonal differences.
During the reproductive cycle of the little brown bat (Myotis lucifugus), the display of sexual behavior is out of synchrony with maximal gonadal development, suggesting that changes in plasma hormone levels per se are not the primary determinants of neural responsiveness. In the present study, we investigated pathways of androgen metabolism in the brain of the bat and compared brain aromatase activity in spring and in autumn. Tissue homogenates were incubated with [3H] androstenedione in the presence of an NADH/NADPH-generating system, and radiolabeled products isolated and their authenticity verified by recrystallization to constant specific activity. Aromatase was identified in preoptic/hypothalamic and adjacent limbic areas, and 5 alpha-reductase was detected in all major brain divisions. No gender-based differences in brain aromatase were seen in spring just prior to emergence from hibernation; however, activity was greater in males than in females when measured during maximal breeding activity in autumn. In addition, seasonal changes were evident in the preoptic/hypothalamic regions of both sexes (spring greater than autumn), although estrone yields from limbic tissues remained constant. Thus, in seasonally breeding species, the rate at which circulating androgen is converted to estrogen or other biologically active metabolites in the brain itself may be an important determinant of behavioral or feedback responsiveness.
D000728:Androgens / Q000378:metabolism*; D000735:Androstenedione / Q000378:metabolism; D000818:Animals; D001141:Aromatase / Q000032:analysis; D001921:Brain / Q000378:metabolism*; D002685:Chiroptera / Q000378:metabolism*; D005260:Female; D008297:Male; D010053:Ovary / Q000378:metabolism; D012621:Seasons; D012737:Sex Factors
D000728:Androgens; D000735:Androstenedione; D001141:Aromatase