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1 July 2002 Relationship of Serum Testosterone Concentrations to Mate Preferences in Rams
Charles E. Roselli, Fred Stormshak, John N. Stellflug, John A. Resko
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Abstract

This study examined systemic testosterone concentrations in rams that were classified according to their sexual behavior and partner preference as either female-oriented (FOR), male-oriented (MOR), or asexual (NOR). For this purpose, we measured testosterone concentrations under three separate conditions: in conscious rams during the nonbreeding season (June) and breeding season (November), and in anesthetized rams during the breeding season. Basal testosterone concentrations in conscious rams were not different among the three groups (P > 0.05) in either season. However, when rams were anesthetized, mean systemic concentrations of testosterone in FORs (mean ± SEM, 13.9 ± 7.4 ng/ml serum) were greater (P < 0.05) than in NORs (0.9 ± 0.1 ng/ml), but not in MORs (2.2 ± 6.2 ng/ml), whereas testosterone concentrations were not different between MORs and NORs (P > 0.05). Concentrations of testosterone in the spermatic vein of FORs (127 ± 66 ng/ml) were greater (P < 0.05) than in MORs (41 ± 10 ng/ml) and NORs (19 ± 7 ng/ml). Serum LH concentrations were not different. Cortisol was higher (P < 0.05) in anesthetized MORs (25.1 ± 4.2 ng/ml) and NORs (27.2 ± 4.4 ng/ml) than in FORs (10.9 ± 1.8 ng/ml). These results demonstrate that circulating testosterone concentrations are related to sexual behavior only when rams are bled under anesthesia. Thus, differences in basal androgen concentrations in adulthood cannot be responsible for expression of male-oriented preferences or low libido in sheep. Instead, functional differences must exist between the brains of rams that differ in sexual preference expression.

Charles E. Roselli, Fred Stormshak, John N. Stellflug, and John A. Resko "Relationship of Serum Testosterone Concentrations to Mate Preferences in Rams," Biology of Reproduction 67(1), 263-268, (1 July 2002). https://doi.org/10.1095/biolreprod67.1.263
Received: 3 November 2001; Accepted: 1 February 2002; Published: 1 July 2002
KEYWORDS
behavior
male sexual function
neuroendocrinology
stress
testosterone
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