Wickings, E. J., Nieschlag, E. 1980. Pituitary response to LRH and TRH stimulation and peripheral steroid hormones in conscious and anaesthetized adult male rhesus monkeys (Macaca mulatta). Acta Endocrinologica 93, 287-293.

Adult male rhesus monkeys are aggressive animals and very difficult to handle. Hence experimental manipulations necessarily involve the use of restraint procedures, either chemical or physical, which may influence endocrine functions. ... The male rhesus monkey, however, is a very aggressive animal and cannot be trained to adapt to experimental situations as easily as the female animal can. Ketamine exerted distinct effects on pituitary function [e.g., prolactin] but not on peripheral concentrations of steroids [e.g., testosterone, cortisol].