Vagal influence on compensatory ovarian growth is important only briefly after hemicastration

Participation of the Cholinergic System in the Development of Polycystic Ovary Syndrome

In rats with polycystic ovary syndrome (PCOS) induced by injection of estradiol valerate (EV), unilateral or bilateral section of the vagus nerve restores ovulatory function in 75% of animals, suggesting that the vagus nerve participates in the development of PCOS. Since the vagus nerve is a mixed nerve through which mainly cholinergic-type information passes, the objective of the present study was to analyze whether acetylcholine (ACh) is involved in the development of PCOS. Ten-day-old rats were injected with 2.0 mg EV, and at 60 days of age, they were microinjected on the day of diestrus in the bursa of the left or right ovary with 100 or 700 mg/kg of ovarian weight atropine, a blocker of muscarinic receptors, and sacrificed for histopathological examination after the surgery. Animals with PCOS microinjected with 100 mg of atropine showed a lack of ovulation, lower serum concentrations of progesterone and testosterone, and cysts. Histology of the ovaries of animals microinjected with 700 mg of atropine showed corpus luteum and follicles at different stages of development, which was accompanied by a lower concentration of progesterone and testosterone. These results allow us to suggest that in animals with PCOS, ACh, which passes through parasympathetic innervation, is an important component in the persistence and development of the pathophysiology.

Unilateral section of the superior ovarian nerve induces first ovulation in the Zucker fatty (fa/fa) rat

Hyperactivity in the sympathetic nervous system has been shown to be related to the development of ovarian pathologies. In addition, obesity has been found to be associated with multiple reproductive anomalies and is considered a chronic stress condition of low intensity with changes in the peripheral sympathetic activity. Therefore, in the present study, we aimed to evaluate if the information reaching the ovaries through the superior ovarian nerve (SON) modifies the ovarian function of Zucker fatty rats. We performed a unilateral section of the SON at 32 days of age and autopsies were carried out on the day of the first vaginal estrus. The results showed that fatty animals do not ovulate on the day of the first vaginal estrus and exhibit an increase in catecholaminergic fibers and the presence of precystic structures in the ovaries, without changes in the onset of puberty or in the secretion of ovarian and hypophyseal hormones. We also found that the section of the right SON resulted in ovulation on the day of the first vaginal estrus, which was accompanied by a decrease in ovarian noradrenaline content. The section of the left SON caused a delay in puberty without changes in the rest of the parameters. These results provide functional evidence that the peripheral sympathetic innervation participates in the regulation of ovarian functions in an animal model of genetic obesity.

In Adult Rats With Polycystic Ovarian Syndrome, Unilateral or Bilateral Vagotomy Modifies the Noradrenergic Concentration in the Ovaries and the Celiac Superior Mesenteric Ganglia in Different Ways

In rats with polycystic ovarian syndrome (PCOS) induced by estradiol valerate (EV) injection, sectioning of the vagus nerve in the juvenile stage restores ovulatory function, suggesting that the vagus nerve stimulates the onset and development of PCOS. We analyzed whether in adult rats, the role played by the vagus nerve in PCOS development is associated with the nerve’s regulation of noradrenergic activity in the celiac superior mesenteric ganglion (CSMG). Ten-day-old rats were injected with corn oil [vehicle (Vh)] or EV (2 mg). At 76 days of age, rats injected with Vh or EV were subjected to sham surgery or the sectioning of one or both vagus nerves (vagotomy). The animals were sacrificed at 80–82 days of age at vaginal estrus smear. Compared to Vh-treated animals, EV-induced PCOS rats showed a lack of ovulation, the presence of follicular cysts, and a high concentration of testosterone, without changes in noradrenaline concentrations in the CSMG or ovaries. In PCOS rats, sham surgery lowered serum testosterone and noradrenaline concentrations in the CSMG but did not restore ovulation. In animals with PCOS, vagotomy lowered testosterone concentrations to a larger degree than in sham-surgery animals. The ovaries of rats with PCOS and vagotomy showed fresh corpora lutea, indicating ovulation. In EV-treated rats with unilateral vagotomy, the concentration of noradrenaline in the CSMG was similar to that in rats with PCOS and sham surgery, which did not ovulate, while in the ovaries of PCOS rats with left or bilateral vagotomy, the noradrenaline concentration was lower than that in sham-surgery-treated animals. Our results suggest that the vagus nerve regulates PCOS development through a different mechanism than the increase in the noradrenergic activity in the CSMG; however, in ovaries, the restoration of ovulation is associated with a decrease in ovarian noradrenaline.

The effects of sensorial denervation on the ovarian function, by the local administration of capsaicin, depend on the day of the oestrous cycle when the treatment was performed

There is evidence that sensory innervation plays a role in the regulation of puberty. The present study investigates the effects of functional sensorial desensitisation induced by capsaicin administration to adult female rats in the days of diestrus 1, diestrus 2, pro-oestrus or oestrus on ovulation and serum oestradiol and progesterone concentration. The animals were allotted at random to one of the following groups: (1) animals with capsaicin administration into the bursa ovarica (local administration) (2) animals with vehicle administration into the bursa ovarica and (3) untreated animals group. The animals treated were killed on the day of oestrus after three consecutive 4-day oestrous cycles. No differences were observed in oestrous cyclicity or the average number of ova shed between the sensorial desensitisation animals and the vehicle-treated groups. Capsaicin administration resulted in a significant increase in the intra-ovarian noradrenaline levels in the day of diestrus 2 and pro-oestrus. Serum oestradiol and progesterone concentrations were different, depending on the day of the oestrous cycle in which the treatment was performed. These results suggest that in adult normal female rats, ovarian sensorial innervations participate together with the sympathetic innervation in the ovarian function regulating the hormone secretion and this participation varies along the oestrous cycle.

Low-dose gold nanoparticles exert subtle endocrine-modulating effects on the ovarian steroidogenic pathway ex vivo independent of oxidative stress

Gold nanoparticles (GNPs) have gained considerable attention for application in science and industry. However, the untoward effects of such particles on female fertility remain unclear. The objectives of this study were to (1) examine the effects of 10-nm GNPs on progesterone and estradiol-17β accumulation by rat ovaries ex vivo and (2) to identify the locus/loci whereby GNPs modulate steroidogenesis via multiple-reference gene quantitative real-time RT-PCR. Regression analyses indicated a positive relationship between both Star (p < 0.05, r(2) = 0.278) and Cyp11a1 (p < 0.001, r(2) = 0.366) expression and P4 accumulation upon exposure to 1.43 × 10(6) GNPs/mL. Additional analyses showed that E2 accumulation was positively associated with Hsd3b1 (p < 0.05, r(2) = 0.181) and Cyp17a1 (p < 0.01, r(2) = 0.301) expression upon exposure to 1.43 × 1(3) and 1.43 × 10(9) GNPs/mL, respectively. These results suggest a subtle treatment-dependent impact of low-dose GNPs on the relationship between progesterone or estradiol-17β and specific steroidogenic target genes, independent of oxidative stress or inhibin.

Effects of acute unilateral ovariectomy to pre-pubertal rats on steroid hormones secretion and compensatory ovarian responses

In the present study we analyzed the existence of asymmetry in the secretion of steroid hormones in pre-pubertal female rats treated with unilateral ovariectomy (ULO) or unilateral perforation of the abdominal wall (sham-surgery). Treated rats were sacrificed at different times after surgery. Since sham-surgery had an apparent effect on the age of first vaginal estrous (FVE) and serum levels hormone, the results of the sham surgery groups were used to assess the effects of their respective surgery treatment groups. On the day of FVE, compensatory ovulation (CO) and compensatory ovarian hypertrophy (COH) were similar in animals with ULO, regardless of the ovary remaining in situ. In ULO treated animals, progesterone (P4) levels were higher than in animals with sham-surgery one hour after treatment but lower in rats sacrificed at FEV. Left-ULO resulted in lower testosterone (T) concentration 48 and 72 hours after surgery. In rats with Right-ULO lower T concentrations were observed in rats sacrificed one or 72 hours after surgery, and at FVE. ULO (left or right) resulted in lower estradiol (E2) concentrations one or 72 hours after treatment. In rats with Left-ULO, E2 levels were higher 48 hours after surgery and at FVE. Left-ULO resulted in higher levels of follicle stimulating hormone (FSH) five hours after surgery and at FVE. FSH levels were higher in rats with Right-ULO sacrificed on FVE. The present results suggest that in the pre-pubertal rat both ovaries have similar capacities to secrete P4, and that the right ovary has a higher capacity to secrete E2. Taken together, the present results support the idea that the effects of ULO result from the decrease in glandular tissue and changes in the neural information arising from the ovary.

Ipsilateral vagotomy to unilaterally ovariectomized pre-pubertal rats modifies compensatory ovarian responses

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.

Involvement of the peripheral cholinergic muscarinic system in the compensatory ovarian hypertrophy in the rat

In the present experiments, unilateral ovariectomy (ULO) induced compensatory hypertrophy (COH) of the remaining rat ovary (60%-85% increase in ovarian weight, total proteins, and total RNA and DNA). An increased thymidine uptake preceded the organ enlargement. COH was inhibited by i.p.-administered muscarinic antagonist propantheline (dose-dependently) or botulinum toxin delivered locally to the ovary. The effects were reversed by bethanecol i.p. (a muscarinic agonist). In sham ULO animals, [3H]-scopolamine binding to ovarian membranes indicated the existence of muscarinic receptors (Kd 2.5 nM, Bmax 12 fmol/mg proteins, Hill 1.0). The ovarian 1,2-diacylglycerol (DAG) was 120-150 pmol/mg tissue and did not react to carbachol in vitro (50 microM). At 15 minutes after ULO, the [3H]-scopolamine binding was unchanged (Kd 2.6 nM, Bmax 12.6 fmol/mg tissue, Hill 1.0), but the ovarian DAG was increased (280-350 pmol/mg tissue) and increased further in response to carbachol (460-550 pmol/mg tissue). After ULO, ovarian DAG remained continuously responsive to carbachol. The ULO-induced DAG increase and enhanced susceptibility to carbachol were inhibited by the botulinum toxin or atropine pretreatments. Abdominal vagotomy done immediately before ULO also inhibited the ULO-induced DAG increase and DAG responsiveness to carbachol. However, when the vagotomy was performed 10 mins after ULO, the ovarian DAG remained responsive to carbachol in vitro. The data suggest that the peripheral cholinergic system, including the ovarian muscarinic receptors, stimulates COH. This is apparently associated with the ULO-induced coupling of the ovarian muscarinic receptors to phosphoinositide (PI) breakdown. Vagus plays a role in the occurrence of the changed muscarinic receptor-PI breakdown relationship in the remaining ovary.

Unilateral or bilateral vagotomy performed on prepubertal rats at puberty onset of female rat deregulates ovarian function

BACKGROUND

Injecting a neurotoxin virus into ovary of adult rats has provided morphologic evidence of a multisynaptic neural pathway between ovary and central nervous system (CNS). Vagus nerve is one of the pathways used by CNS to send and receive information to and from the ovary.

METHODS

The present study analyzed whether or not vagal innervation of ovaries in prepubertal rats modulated, in a stimulatory fashion, functions of the ovary and whether the modulating function of these nerves was asymmetric.

RESULTS

Animals vagotomized at 24 and 28 days of age showed delay in age of onset of puberty. Unilateral or bilateral vagotomy performed at 24 days of age did not modify ovulation rates or number of ova shed. In turn, bilateral vagotomy performed at 28 days of age resulted in a significant increase in number of ova shed by ovulating animals. Unilateral and bilateral vagotomy performed on day 24 or 28 resulted in a decrease in estradiol serum levels. Unilateral vagotomy performed on 24-day-old rats did not modify progesterone levels, while bilateral vagotomy on the same age group resulted in a significant increase of progesterone levels. In turn, unilateral and bilateral vagotomy performed on rats aged 28 days resulted in lower progesterone levels.

CONCLUSIONS

Present results confirmed results of previous studies, indicating that interrupting ovarian innervation had an effect on regulation of ovarian functions by CNS and that these effects varied according to age at which denervation was performed.

Capsaicin-sensitive adrenal sensory fibers participate in compensatory adrenal growth in rats

Compensatory adrenal growth, in which one gland undergoes hyperplasia after removal of the other, is mediated by a neural reflex. In the present studies, a method employing capsaicin to selectively remove adrenal sensory fibers was developed and applied to determine whether adrenal capsaicin-sensitive fibers participate in compensatory adrenal growth. The splanchnic nerves of anesthetized male rats were treated with capsaicin or vehicle. Capsaicin treatment selectively removed adrenal calcitonin gene-related peptide-positive fibers. One week after drug treatment, rats underwent left adrenalectomy or sham surgery and recovered for 5 days. Capsaicin treatment bilaterally or to the left splanchnic nerve alone (i.e., the afferent nerve in the reflex) impaired compensatory adrenal growth at 5 days compared with vehicle controls, whereas capsaicin treatment to the right splanchnic nerve alone did not affect growth. Moreover, left adrenalectomy induced c-Fos immunolabeling in ipsilateral dorsal spinal cord that was prevented by capsaicin treatment. These data suggest that adrenal capsaicin-sensitive afferent nerves participate in compensatory adrenal growth and that this effect is primarily on the afferent limb of the reflex.