Effect of exogenous administration of oxytocin on postpartum follicular dynamics, oestrous rate and ovulation in Nili-Ravi buffaloes

Effects of Chronically Exogenous Oxytocin on Ovary and Uterus: A Comparison of Intraperitoneal and Intranasal Administration

Oxytocin (OT) has been studied as a therapeutic neuropeptide in various diseases, but its effect on the ovary and uterus is not fully known. This study investigates the effects of intranasal and intraperitoneal OT administration on ovaries and uterus in rats. Four experimental groups were created using 7-week-old Sprague Dawley-type female rats: Control (Ctrl), oxytocin-intraperitoneal (0.1µg/day) (OT-IP), oxytocin-intranasal (0.05µg/day) (OT-IN1), and oxytocin-intranasal (0.1µg/day) (OT-IN2). The blood, the ovarian, and the uterus were collected at the end of the 28th day of OT administration. Afterward, histological and biochemical analyses were performed. We observed that the Graaf follicles were higher in both OT-IN2 and OT-IP groups compared to the Ctrl group. Moreover, the corpus luteum was increased only in the OT-IN2 group. Ki-67, CD31, VEGF, and TGF-ß immunostaining showed no significant change in the ovary. In contrast, Ki-67, VEGF, and OTR expressions demonstrated significant alterations in the uterus. Furthermore, TGF-ß immunohistochemistry and the histopathologic score did not reveal the statistical change in the uterus. Serum hormone levels showed that the anti-Müllerian hormone increased in all OT groups vs. the Ctrl. OT-IP showed an increment of follicle-stimulating hormone and estradiol decrement. There was a decrease in serum E2 levels, although the Graafian follicle number increased in OT-IP groups compared to the Ctrl group. However, luteinizing hormone, gonadotropin-releasing hormone, progesterone, testosterone, OT levels, and oxidative stress index did not reveal any statistical difference. Accordingly, the intranasal route may have beneficial effects compared to the intraperitoneal route regarding exogenous OT administration-related studies. In conclusion, we reported that exogenous OT increases the follicle reserve and may cause histological changes in the reproductive system of female rats.

Neurophysiology of Milk Ejection and Prestimulation in Dairy Buffaloes

The present review aims to integrate the anatomical characteristics of the mammary gland and the neurophysiology of milk ejection to understand the milking capacity of the water buffalo. Since one of the main uses of this species is milk production, this article will analyze the controversies on the use of oxytocin as a stimulant during milking as well as the existing alternatives that farmers apply to promote correct stimulation during milk letdown. According to the available literature, the efficiency of the milking process, the quality of the milk, and the health of the animals are elements that require the consideration of species-specific characteristics to enhance the performance of buffaloes. The incorporation of technological innovations and competitive strategies could contribute to a better understanding of water buffalo in the milk industry.

Oxytocin in Women's Health and Disease

Oxytocin (OT) is a nonapeptide mainly produced in the supraoptic and paraventricular nuclei. OT in the brain and blood has extensive functions in both mental and physical activities. These functions are mediated by OT receptors (OTRs) that are distributed in a broad spectrum of tissues with dramatic sexual dimorphism. In both sexes, OT generally facilitates social cognition and behaviors, facilitates parental behavior and sexual activity and inhibits feeding and pain perception. However, there are significant differences in OT levels and distribution of OTRs in men from women. Thus, many OT functions in men are different from women, particularly in the reproduction. In men, the reproductive functions are relatively simple. In women, the reproductive functions involve menstrual cycle, pregnancy, parturition, lactation, and menopause. These functions make OT regulation of women's health and disease a unique topic of physiological and pathological studies. In menstruation, pre-ovulatory increase in OT secretion in the hypothalamus and the ovary can promote the secretion of gonadotropin-releasing hormone and facilitate ovulation. During pregnancy, increased OT synthesis and preterm release endow OT system the ability to promote maternal behavior and lactation. In parturition, cervix expansion-elicited pulse OT secretion and uterine OT release accelerate the expelling of fetus and reduce postpartum hemorrhage. During lactation, intermittent pulsatile OT secretion is necessary for the milk-ejection reflex and maternal behavior. Disorders in OT secretion can account for maternal depression and hypogalactia. In menopause, the reduction of OT secretion accounts for many menopausal symptoms and diseases. These issues are reviewed in this work.