Neonatal DHT but not E2 speeds induction of sexual receptivity in the musk shrew

Abstract

Neural aromatization of testosterone (T) to estrogen during development is thought to be important for sexual differentiation of many altricial mammals. We evaluated the effects of neonatal injections of the non-aromatizable androgen dihydrotestosterone propionate (DHTP) and estradiol (E2) on the copulatory behavior of the female musk shrew, an altricial insectivore. Following adult ovariectomy and replacement T, animals were paired with a stimulus female for two 60-minute copulatory behavior tests. The latency to induce sexual receptivity (in the form of tail-wagging by the female), mount latency and total number of mounts were recorded in experimental females and in a group of untreated control males. While neither hormone treatment significantly affected mounting behavior, DHTP-treated animals induced receptivity faster and with latencies not significantly different from intact males, suggesting that early non-aromatizable androgens can have masculinizing actions by either increasing sexual motivation or making the treated animal more attractive to the stimulus female. Reliance on androgenic rather than estrogenic metabolites for the differentiation of courtship behaviors conforms to the pattern seen more typically in primates than rodents.

Sex difference in Onuf's nucleus homologue in the Asian musk shrew

“…Aspects of sexual differentiation in the musk shrew, specifically the role of reduced testosterone metabolites in behavioral masculinization, more closely resemble primates than laboratory rodents (Ewton et al, 2010). Genetic evidence also suggests that the Asian musk shrew is more closely related to humans than are other common laboratory animals.…”

Identification of the sexually dimorphic gastrin‐releasing peptide system in the lumbosacral spinal cord that controls male reproductive function in the mouse and Asian house musk shrew (Suncus murinus)

“…The Asian house musk shrew, Suncus murinus (suncus named as the laboratory strain), is of the order Eulipotyphla (formerly Insectivora) and thought to resemble specialized placental mammals (eutherians) (Vogel, ). Although many aspects of sexual differentiation and reproductive physiology in suncus are unique, the role of reduced androgens in behavioral masculinization is more similar to primates than to mice and rats (rodents) (Ewton, Siboni, Jackson, & Freeman, ). For instance, suncus is a reflex ovulator (Inoue et al, ); pregnant suncus ovariectomized on Days 6 to 15 of a 30‐day (average gestation period in suncus) and can maintain pregnancy in the absence of ovaries (Hasler & Nalbandov, ).…”