Hormonal Mechanisms Involved in the Control of Oestrous Cycle Duration by the Odour of Urine in the Rat

Abstract

The mechanisms involved in the reduced cycle duration following exposure to the odour of urine were studied in natural and experimental 5-day cyclic female Wistar rats.A decrease in the rate of ovarian progesterone secretion from the morning of dioestrus I to that of dioestrus II was observed in females whose cycle duration was reduced from 5 to 4 days following exposure to the odour of rat urine. No decrease in ovarian progesterone secretion occurred in females maintaining a 5-day cyclicity despite exposure to this odour. An increase in follicular growth was noted in females with cycle duration reduced from 5 to 4 days, when compared with those maintaining a 5-day rhythm. As a result of exposure to the odour of urine no reduced cycle duration occurred in females with cycles lengthened from 4 to 5 days as a result of progesterone injection on dioestrus I of 4-day cycles. Hence the decrease in ovarian progesterone secretion, induced by exposure to the odour of urine, is considered to cause a speeding up in follicular growth, thereby reducing oestrous cycle duration in 5-day cyclic rats.The role of the odour of urine in the regulation of oestrous cycle duration is now well established in the rat. Cooper 8c Haynes ), Cooper et al. (1972) and Purvis et al. (1971 demonstrated in female rats, with lengthened cycles following food restriction, that the presence of the male could result in reduced cycle duration. Likewise, olfactory stimuli may act on normal cyclic female rats. Olfactory bulb deprivation was shown to alter oestrous cycle duration 426

Regionalization of Fos immunostaining in rat accessory olfactory bulb when the vomeronasal organ was exposed to urine

“…In female rats, pheromones in urine excreted from males and females induce various changes in gonadal functions, including reflex ovulation in the absence of coitus and mounting ( Johns et al . 1978 ), a reduction in the oestrous cycle of female rats from 5 to 4 days ( Chateau et al . 1976 ), and restoration of the oestrous cycle that has been inhibited by treatment with oestradiol ( Mora & Cabrera 1997).…”

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

“…The pregnancy block has not been observed in rats. In rats, pheromones in the urine of males reduced the oestrous cycle of females from 5 to 4 d 2) and induced the dioestrous stage and restored oestrous cycles in irregularly cycling and anovulatory persistent-oestrous aging females. 21) Baseline plasma progesterone concentrations in irregularly cycling and anovulatory-oestrous females were similar to those in normally cycling 7-8-month-old females; male urinary pheromones increased the levels of plasma progesterone in these females.…”

“…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.…”

“…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.…”

Age-Dependent Spatial Distribution of Bromodeoxyuridine-Immunoreactive Cells in the Main Olfactory Bulb

“…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, 15) and a reduction in the oestrous cycle of female rats from 5 to 4 d, 16) and oestrous synchrony among female rats housed together.17) The VNO exists in many vertebrates for the purpose of receiving pheromones, which in turn affect sexual and social behavior. 18,19) Vomeronasal sensory neurons project to the AOB located on the dorso-caudal surface of the MOB.…”