Increases in Plasma Concentration of Progesterone by Protease-Sensitive Urinary Pheromones in Female Rats

Abstract

Various gonadal functions of females are controlled by pheromones in many vertebrates. Pheromones have been found in saliva, skin gland secretions, and urine. For example, pheromones in the urine excreted from male and female rats induce various changes in gonadal function and endocrine state, including reflex ovulation in the absence of coitus and mounting, 1) and a reduction in the oestrous cycle of female rats from 5 to 4 d, 2) and oestrous synchrony among female rats housed together.3) The vomeronasal organ exists in many vertebrates for the purpose of receiving pheromones, which in turn affect sexual and social behavior. 4,5) In a previous study, we demonstrated that the sensory neurons in the vomeronasal organ (VNO) of female rats, which respond to male Wistar urine, are localized in the apical layer of the epithelium, where one type of G i2a is selectively expressed.6) Exposure of the VNO of the female Wistar rat to male Wistar urine induces c-Fos expression, which is correlated with cellular activity, primarily in the rostral region of the accessory olfactory bulb (AOB), 7) suggesting that pheromonal information received by the sensory neurons in the VNO is transmitted to neurons in the AOB. Exposure of the VNO of female rats to protease-sensitive urinary pheromones excreted from male rats induced the expression of c-Fos-immunoreactive cells in the AOB. 8) In the present study, in order to characterize the effects of protease-sensitive pheromones present in male urine on the endocrine state of female rats, the plasma progesterone concentration in female rats was measured after the female rats had been exposed to male urinary pheromones with and without protease treatment. MATERIALS AND METHODS AnimalsAll experiments were carried out in accordance with the Guidelines for the Use of Laboratory Animals of the Graduate School of Pharmaceutical Sciences, Hokkaido University. The Wistar rats were obtained from Sankyo Laboratory Co., Sapporo, Japan. The animals were housed in samesex groups of four in a room that was maintained at a temperature of 22Ϯ0.5°C, with a relative humidity of 58%, and on a 14-h light/10-h dark cycle (lights off at 21:00). The males and females were housed in the same room. All rats had free access to food and water. Three or four rats were subjected to each condition. The oestrous cycle was determined based on the observation of fresh vaginal smears of female Wistar rats (less than 6 months old) at 15:00. The following criteria were used to define the oestrous and dioestrous stages on a 4-day cycle: oestrous was identified by a smear of cornified cells, and dioesterous was identified by leucocytes in the presence of nucleated epithelial cells. Stimulation with Urine PreparationsThe noses of adult female rats from the Wistar strain were subjected to a spray of urine preparations from male Wistar rats or a control salt solution. The unanesthetized rats were gently held by hand for 50 min during the spraying of urinary samples (30 ml). Urine was collected from four or five one-year-old Wi...

Neonatal handling induces alteration in progesterone secretion after sexual behavior but not in angiotensin II receptor density in the medial amygdala: Implications for reproductive success

“…Pre-ejaculatory intromissions are also necessary for the successful transport of spermatozoa into the uterine lumen (Chester and Zucker, 1970). However, it has been demonstrated that after exposure to male urine, the female rats present an increased plasma progesterone (Mora and Sánchez-Criado, 2004;Tomioka et al, 2005). Possibly the neonatally handled female rats are less sensitive to male pheromones.…”

Rat Mammary carcinoma susceptibility 3 (Mcs3) pleiotropy, socioenvironmental interaction, and comparative genomics with orthologous human 15q25.1-25.2

“…Male pheromones are known to induce physiological and hormonal changes in the female endocrine and reproductive system ( Rekwot et al 2001 ). For example, male urinary pheromones have been demonstrated to increase plasma-luteinizing hormone and progesterone levels in females ( Tsai et al 1994 ; Tomioka et al 2005 ). The endocrine system has a role in body weight regulation.…”