Increases in testosterone levels and in copulatory behavior of male rhesus monkeys following treatment with human chorionic gonadotrophin

Abstract

The sexual behavior of five male rhesus monkeys was observed before, during, and after administration of human chorionic gonadotropin (HCG) sufficient to induce increases in serum testosterone. Each male was given 12 half-hour pair tests with an estrogen-implanted ovariectomized female during each of the three phases of the study (Pretreatment, Treatment, Post-treatment). Summaries of selected categories of sexual and other social behaviors were tabulated for each phase of the study. Grooming, mount latency, and ejaculation frequency, as well as other behavioral measures, were unaffected by hormone treatment. However, latency to ejaculation decreased by 40% ( P < 0.01) and mount rate increased by 71% ( P < 0.05) during hormone administration. Sexual presentations by the female decreased by 38% ( P < 0.05). Limb shaking decreased 55% during HCG treatment ( P < 0.05). These findings demonstrate that increases in testosterone secretion subsequent to gonadotrophin injection in intact male rhesus monkeys can produce significant alterations in male and female sexual behavior.