Abstract
The present study evaluates the participation of the vagus nerve in pre-pubertal rats with unilateral ovariectomy on puberty onset, and on progesterone, testosterone and estradiol serum levels, and the compensatory responses of the ovary. Unilateral vagotomy did not modify the onset of puberty in unilaterally ovariectomized rats. Ovulation rates of animals with the left vagus nerve sectioned and the left ovary in-situ was lower than in rats with only unilateral ovariectomy. Sectioning the left vagus to 32-day old rats with the left ovary in-situ resulted in lower compensatory ovarian hypertrophy than in rats with right unilateral ovariectomy. Twenty-eight or 32-day old animals with sectioning of the right vagus nerve and the right ovary in situ showed higher compensatory ovulation. Twenty-eight -day old rats with the right ovary in situ had higher progesterone and testosterone levels than animals of the same age with the left ovary in-situ. Compared to animals with the right ovary in situ, animals treated at 32-days of age, sectioning the ipsi-lateral vagus nerve resulted in higher progesterone levels. Higher progesterone levels were observed in 28- and 32 days old rats with the left ovary in situ and left vagus nerve sectioned. Thirty-two day old animals with the right ovary in situ and right vagus nerve sectioned had higher progesterone levels than rats of the same age with the left ovary in situ and left vagus nerve sectioned. Left vagotomy to 28-day old rats with the left ovary in situ resulted in higher testosterone levels, a reverse response to that observed in animals with sectioning of the right vagus and the right ovary in situ. Thirty-two day old rats with the left ovary in situ and left vagus nerve sectioned showed lower testosterone levels than animals without vagotomy and with the left ovary in situ.Twenty-eight -day old animals with the left vagus sectioned and left ovary in situ had lower estradiol serum levels than rats without unilateral vagotomy, a response similar to that observed in 32-day old rats with the right ovary in situ and right vagus nerve sectioned.Present results suggest an asymmetric regulation of steroid hormones secretion by the vagus nerve innervations in animals with unilateral ovariectomy, and those differences in testosterone serum levels observed are associated to the ovary remaining in-situ, vagal innervation and age when the animals were treated.
Highlights
The vagus nerve is one of the neural pathways involved in regulating ovarian functions [1,2,3,4,5,6,7,8,9] Gerendai and collaborator's provided the first morphological evidence of a multi-synaptic neural pathway between the ovary and the central nervous system (CNS), showing that the vagus nerve forms part of such neural connection [6,7,10]
Ovulation rate in rats with the ovary extirpated immediately after sectioning the ipsilateral vagus nerve Compared to animals with unilateral ovariectomy (ULO), extirpating the right ovary to 28 or 32-day old rats with left vagotomy resulted in lower ovulation rates (Figure 1A); while the reverse
The results suggest that the ovaries' vagus nerve innervations modulate hormone secretion in an asymmetric way, and the hormone secretion is related to both, which ovary remains in situ, and the age of the animals when ULO treatment is performed
Summary
The vagus nerve is one of the neural pathways involved in regulating ovarian functions [1,2,3,4,5,6,7,8,9] Gerendai and collaborator's provided the first morphological evidence of a multi-synaptic neural pathway between the ovary and the central nervous system (CNS), showing that the vagus nerve forms part of such neural connection [6,7,10]. COH results in the rise of the follicle population and a decrease in the rate of follicular atresia [13]. These effects have been explained as resulting from lower systemic ovarian steroid levels that partially remove the negative feedback over the hypothalamic-pituitary axis, triggering a higher release of gonadotropins [14,15]. We showed that increasing and maintaining elevated levels of follicle stimulating hormone (FSH) in serum does not always result in ovarian weight increase and higher ovulatory responses by the in situ ovary [16]. Modifications in FSH and luteinizing hormone (LH) serum levels, as well as changes in the number of ovulatory follicles induced by extirpating one ovary depend on the day of the estrous cycle when surgery is performed and on the time elapsed between treatment and autopsy [16]
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