Direct electrical stimulation of the superior ovarian nerve in rats causes an increase in neuronal activity in the ipsilateral ovarian plexus nerve

Structural organization of the neuronal pathways of the superior ovarian nerve in the rat

BACKGROUND

In the rat, studies have shown that ovary innervation arrives via the superior ovarian nerve (SON) and the ovarian plexus nerve, which originates from the celiac plexus (CP). In the present study, we performed a neuroanatomical technique to investigate the anatomy of the SON between the ovary and the CP.

RESULTS

We found that the SON fibers were concentrated on the lateral border of the suprarenal ganglion and projected towards, then inserted into the suspensory ligament. Then, it ran parallel to the long axis of the ligament to reach and innervate the ovaries. At this level, the SON was composed of two coiled nerve fibers, each between 10 and 15 µm in diameter. The SON was linked to three different ganglia: the suprarenal ganglia, the celiac ganglia, and the superior mesenteric ganglion.

CONCLUSIONS

The postganglionic fibers that project to the ovary via the SON emerge from the suprarenal ganglia. The trajectories on the right and left sides to each ovary are similar. The somas of ipsilateral and contralateral SON neurons are located in the prevertebral ganglia, mostly in the celiac ganglia.

Neonatal superior ovarian nerve transection inhibits follicle development by enhancing follicular atresia and suppressing granulosa cell proliferation in rats

The ovarian sympathetic nerves participate in the regulation of mammalian ovarian function, but it is still not known whether the neonatal ovarian sympathetic nerve is involved in follicular development and related mechanisms. In the present study, the superior ovarian nerve (SON) of the neonatal rat was transected on postnatal day (PD) 2, and follicle development, ovarian hormone secretion, ovulation rate, granulosa cell proliferation and apoptosis were analysed on PD 30 and PD 90. The results demonstrate that SON transection decreases follicle number and size, reduces ovulation induced by gonadotrophin and enhances follicular atresia. Bromodeoxyuridine (BrdU) and cleaved caspase-3 immunohistochemistry staining provide evidence that SON transection inhibits granulosa cell proliferation and promotes granulosa cell apoptosis. In addition, SON transection increases serum oestradiol levels, but has no influence on serum progesterone levels. These results suggest that the sympathetic nerve supply to the ovaries is important in regulating follicle development and ovary function. These results are critical for further understanding of the neuroendocrine regulation of ovary development and function, although the mechanism needs to be elucidated in future studies.

Superior ovarian nerve (SON) transection leads to stunted follicular maturation: a histomorphologic and morphometric analysis in the rat model

Histomorphologic and morphometric effects of peripubertal superior ovarian nerve (SON) transection were evaluated during adult life in rats. Twenty Sprague-Dawley rats were randomly divided into two groups: the SON-transected (SON-t) group (n = 10) and the sham-operated control group (n = 10). Total follicle development was not influenced; however, follicular maturation was seriously stunted by the procedure, as evidenced by significantly thinner theca interna and follicular wall.

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.

The acute asymmetric effects of hemiovariectomy on testosterone secretion vary along the estrous cycle. The participation of the cholinergic system

The presence of asymmetry in the capacity of the left and right ovaries to secrete testosterone was analyzed by studying the effects of hemiovariectomy along the estrus cycle one hour after surgery. The effects of ether anesthesia on hormone serum levels were also analyzed. Bilateral ovariectomy and the extirpation of the left ovary performed on the day of proestrus resulted in significantly lower testosterone levels. Compared to the anesthetized group, the effects of perforating the peritoneum unilaterally varied according to the day of the estrous cycle and the side of the peritoneum surgery was performed on. Injecting atropine sulfate (ATR) to control or anesthetized rats on D1 resulted in a significant increase of testosterone serum levels. The effects of perforating the peritoneum on testosterone levels depended on the cholinergic innervation and varied along the estrous cycle. Blocking the cholinergic system before performing unilateral or bilateral ovariectomy had different effects depending on the day of the estrous cycle. Testosterone plasma levels increased significantly when surgery was performed on the day of diestrus and dropped when surgery was performed on proestrus. Similar effects were observed when the left adrenal was extirpated from animals with the cholinergic system blocked. The results presented herein support the hypothesis of asymmetry in the ovaries' abilities to secrete steroid hormones, and that the capacity to secrete testosterone varies along the estrous cycle.

Ascending spinal pathways from sexual organs: effects of chronic spinal lesions

A recent survey of paraplegics indicates that regaining sexual function is of the highest priority for both males and females (Anderson, K.D. (2004) Targeting recovery: priorities of the spinal cord-injured population J. Newrotrauma, 21: 1371-1383). Our understanding of the neural pathways and mechanisms underlying sexual behavior and function is limited at the present time. More studies are obviously needed to direct experiments geared toward developing effective therapeutic interventions. In this chapter, a review of studies on the processing of sensory inputs from the male and female reproductive organs is presented with a review of what is known about the location of ascending spinal pathways conveying this information. The effect of spinal cord injury on sexual function and the problems that ensue are discussed.

The participation of the cholinergic system in regulating progesterone secretion through the ovarian-adrenal crosstalk varies along the estrous cycle

This study was designed to analyze the acute effects of unilateral or bilateral ovariectomy or adrenalectomy, performed on different days of the estrous cycle, on progesterone (P4) serum levels 1 h after surgery. The effects of blocking the cholinergic system by injecting atropine sulfate were also analyzed. Ether anesthesia treatment on diestrus 1 (D1) increased P4 serum levels. Compared to right sham-operated animals, right ovariectomy (left ovary in situ) performed on diestrus 2 (D2) or proestrus (P), resulted in P4 serum levels increase. Compared to animals with left sham surgery, left adrenalectomy (right adrenal in situ) performed on P day resulted in significantly lower P4 concentrations. Bilateral adrenalectomy resulted in a significant drop of P4 serum levels; the most remarkable drop was observed in animals treated on D2. Bilateral ovariectomy performed on D1 resulted in lower P4 serum levels, and the same treatment performed on P resulted in a significant rise of P4 serum levels. Injecting atropine sulfate to untouched (control group) rats resulted in significantly higher P4 concentrations. Blocking the cholinergic sys-tem on D1 or P to rats with the right adrenal removed resulted in lower P4 serum levels; while, in contrast, atropine sulfate treatment performed on D2 resulted in P4 serum levels increase. The results support the hypothesis of asymmetry in the ovaries' and adrenals' capacities to secrete P4; that this capacity varies along the estrous cycle; and that P4 secretion by the ovaries and adrenals is regulated by the cholinergic system.

Asymmetric effects of acute hemiovariectomy on steroid hormone secretion by the in situ ovary

The acute effects of hemiovariectomy on progesterone, testosterone, estradiol, and luteinizing hormone (LH) concentrations in serum were studied in rats under the following experimental conditions: control, shamoperated (left or right), hemiovariectomized, bilateral adrenalectomized, and hemiovariectomized plus bilateral adrenalectomized. One-hour after surgery, the concentration of progesterone and testosterone in the serum of right-side sham-operated rats was significantly higher than in control animals. Testosterone concentration in serum in rats with the right ovary in situ was higher than in sham-operated animals; injecting atropine sulfate 1 h before surgery blocked such increase, while the same treatment to rats with the left ovary remaining in situ resulted in a significant increase of testosterone concentration. Adrenalectomy resulted in an increase of testosterone concentration, which was higher when atropine sulfate was injected before surgery. Our results support the idea that left and right ovaries play different roles in the regulation of hormone secretion, and that such differences are related to ovarian innervation.

Role of the central and peripheral nervous system in the ovarian function

This review attempts to give a comprehensive overview of ovarian innervation, considering the whole nervous system and its different levels that may modify the ovarian function. The connection between the ovary and the central nervous system through the autonomic pathways, including the peripheral ganglia, is highlighted. The evidence obtained over the last years highlights the role of the superior ovarian nerve (SON) in the ovarian phenomena. Besides, the effect on the ovary of conventional neurotransmitters and others such as indolamines and peptides, which have been found in this organ, are discussed. Various reproductive diseases have been studied almost exclusively from the endocrine point of view. It is evident that a better knowledge about the role of the neural factors involved in the ovarian physiology may facilitate the understanding of some of these. A review of the concepts and an update of some experimental designs is made that permits clarifying several aspects of the relationship between the neural system and the ovary. At present, there is no doubt that the innervation of the ovary is involved in several physiological aspects of this gland function. However, the relationship of some levels of the nervous system and the ovary offer a wide avenue for future research.

Neonatal superior ovarian nerve transection disturbs the cyclic activity of the female rats

The neural pathway most related with ovarian steroidogenesis has been identified as the superior ovarian nerve (SON). This work constitutes the first study of the effects of early ovarian SON transection, which was performed in rats of 4 days of age (SON-t rats) to magnify the effects of the denervation. The rats were studied at the prepubertal (30 days), peripubertal (41 days) and adult cyclic in dioestrus (60 days) reproductive stages. The SON-t rats showed a delay of vaginal opening, a notable disruption of oestrous cyclicity, and a large number of corpora lutea. In all the stages, the circulating levels of FSH, prolactin and growth hormone were lower in SON-t rats than in controls, whereas LH did not vary. Serum androstenedione levels were higher in SON-t rats at 30 days and lower at 41 days, compared with control animals while no difference was observed at 60 days. Serum progesterone levels did not differ between control and SON-t, but serum oestradiol concentrations were higher in SON-t rats in all of the stages. At the peripubertal stage, there were fewer ovarian beta-adrenergic receptors in SON-t ovaries, associated with a rise in the ovarian content of norepinephrine, but no changes were observed in SON-t rats at 30 and 60 days with respect to the controls. The release of progesterone in vitro from luteal cell in SON-t rats at 60 days was reduced in basal condition and under ovine LH or FSH stimulation, when compared with control animals; while no difference was observed in presence of isoproterenol or androstenedione in the culture medium. In corpora lutea of SON-t rats at 60 days, no change was observed in the activity of 3beta-hydroxysteroid dehydrogenase (3beta-HSD), but the activity of 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) was reduced, suggesting abnormal luteolysis in spite of the large number of corpora lutea. The interruption of innervation at an early age by SON transection is very important in the regulation of ovarian development in prepubertal and cyclic rats. The functional changes observed in the ovary suggest a possible alteration in the hypothalamic-hypophyseal axis.

Effects of guanethidine administration on compensatory ovarian hypertrophy, compensatory ovulation and follicular development in the prepubertal female guinea pig

We analyzed the participation of sympathetic ovarian innervation in the prepubertal female guinea pig on regulation of compensatory ovarian hypertrophy (COH) and compensatory ovulation at puberty. The COH of the left ovary was significantly higher that of the right one (left ovary: 41.5+/-5.2 vs. 27.5+/-5.6%, p<0.05, Kruskal-Wallis test). The sympathetic denervation induced by guanethidine administration beginnings at birth or on day 10 resulted in a significant increase of the COH by each ovary (p<0.05, Kruskal-Wallis test). Only one of the six untreated control guinea pigs sacrificed at the follicular phase ovulate. All the hemiovariectomized animals with the left ovary in situ ovulated, while only two out of five with the right ovary in situ did (100 vs. 40%: p<0.001, Kruskal-Wallis test), unlike the denervated animals, which did not ovulate. The number of corpora lutea present in the ovaries was similar among all groups of animals. These results demonstrate differences in the follicular diameter in untreated female guinea pigs and add further support to the concept of asymmetrical response of the ovaries to denervation.