Plasma androgen and gonadotropin levels during hibernation and testicular maturation in golden-mantled ground squirrels.
The 4-5-mo hibernation season of golden-mantled ground squirrels consists of extended torpor bouts interspersed with brief, periodic intervals of normothermic arousal. Plasma levels of testosterone (T), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) and degree of scrotal pigmentation were measured in torpid and aroused male ground squirrels throughout a season of hibernation and in active animals after the termination of torpor. T was basal in torpid animals; beginning 3 weeks before torpor ended, T was elevated in normothermic males during the first half of periodic arousals but returned to basal levels before animals reentered torpor. After the last (terminal) arousal from torpor, T levels were moderately elevated for 4 wk and maximal for the next 6 wk before they returned to basal values. LH patterns were similar to those of T; however, levels of T and LH were positively correlated only in aroused or posthibernation males. FSH levels remained constant and low during most of the heterothermic season but increased in several torpid males within 3 days of terminal arousal. FSH levels peaked 2 wk after the end of heterothermy. Scrotal pigmentation developed over the first 4 wk after terminal arousal. Maturation of reproductive function occurs during the 4 wk after termination of heterothermy, but elevated levels of T during arousals and variable levels of FSH in the last days of torpor suggest that activation or increased sensitivity of the hypothalamic-pituitary-gonadal axis is important in the termination of heterothermy in ground squirrels.
Barnes
B M
BM
Department of Psychology, University of California, Berkeley 94720.
Kretzmann
M
M
Zucker
I
I
Licht
P
P
D000728:Androgens / Q000097:blood*; D000818:Animals; D006062:Gonadotropins / Q000097:blood*; D006605:Hibernation; D008297:Male; D010902:Pituitary Gland / Q000502:physiology; D012589:Sciuridae; D013091:Spermatogenesis; D013737:Testis / Q000254:growth & development* / Q000502:physiology; D013739:Testosterone / Q000097:blood
D000728:Androgens; D006062:Gonadotropins; D013739:Testosterone