Influence of hypothalamic‐pituitary‐adrenocortical hormones on reproductive hormones in gray wolves ( Canis lupus )

• Published in: Journal of Experimental Zoology
• Main Authors: Kreeger, Terry J., Seal, Ulysses S., Plotka, Edward D.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1992
• Subjects: Animal Science and Zoology; General Medicine; Canis lupus
• Online Access: http://dx.doi.org/10.1002/jez.1402640106; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjez.1402640106; https://onlinelibrary.wiley.com/doi/pdf/10.1002/jez.1402640106

Abstract The release of hypothalamic‐pituitary‐adrenocortical hormones was studied in intact and neutered gray wolves ( Canis lupus ) to determine how these hormones interact and affect reproductive hormones. Experiments were performed on adult wolves anesthetized with 400 mg ketamine and 50 mg promazine. Intravenous (i.v.) injections with 50 μg ovine corticotropin releasing factor (oCRF) significantly increased adrenocorticotropin (ACTH; P ≤ 0.01), cortisol (CORT; P ≤ 0.004), and progesterone ( P ≤ 0.036), but not β‐endorphin ( P ≥ 0.52). Since neutered wolves demonstrated dose‐dependent elevations in response to ACTH, it was concluded that the progesterone was secreted from the adrenal gland. Basal luteinizing hormone (LH) concentrations in neutered wolves were similar before and 60 min after i.v. injection of 1, 5, or 25 IU ACTH ( P ≥ 0.36) or 2.2 mg/kg cortisol ( P = 0.42). Neither 25 IU ACTH ( P = 0.55) nor 0.22 mg/kg dexamethasone ( P = 0.49) altered the LH response to injection of LH releasing hromone in neutered wolves. Chronic administration of 0.22 mg/kg/day dexamethasone for 3 d did not alter baseline LH concentration ( P = 0.75). Injection of 1.0 mg/kg naloxone (NAL), however, increased LH concentrations relative to baseline values in both intact ( P = 0.032) and neutered ( P = 0.0005) female wolves, but no in intact ( P = 0.19) or neutered males ( P = 0.07). These results indicated that in gray wolves (1) oCRF stimulated the release of pituitary and adrenal hormones in a fashion similar to that of other mammals; (2) the adrenal cortex was capable of secreting progesterone into the systemic circulation; (3) exogenous glucocorticoids did not alter LH concentrations; and (4) endogenous opioids may modulate LH secretion in female wolves. © 1992 Wiley‐Liss, Inc.