Injections of horseradish peroxidase (HRP) into the right or left ovary of the rat produced labeling of perikarya in both nodose ganglia and ipsilateral dorsal root ganglia (DRGs) from T10 to L2. The greatest concentration of labeled cells was in T13 and L1, DRGs. It is suggested that visceral afferent fibers from the ovary may mediate visceral reflexes that modulate ovarian function.

Following unilateral ovariectomy in the rat, the remaining ovary undergoes rapid compensatory changes including an increase in the number of antral follicles (follicular activation) and an increase in ovarian weight (compensatory ovarian hypertrophy). The ovary is innervated by the vagus nerve (Burden et al., 1983). In the present study, the effects of right and left cervical vagotomy and abdominal vagotomy on follicular activation and compensatory ovarian hypertrophy in the remaining right or left ovary were compared 15 days after unilateral ovariectomy. Neither right nor left cervical vagotomy affected compensatory ovarian hypertrophy of the right or left ovaries but abdominal vagotomy depressed compensatory ovarian hypertrophy in both the right and left ovaries. Left cervical vagotomy did not inhibit follicular activation, but right cervical vagotomy prevented follicular activation in the right but not left ovary. Also, abdominal vagotomy inhibited follicular activation in the right but not the left ovary. In animals with both ovaries which were subjected to the left or right cervical vagotomy or abdominal vagotomy follicular counts in both right and left ovaries were similar. Collectively, these data indicate that the vagus nerve participates in follicular activation after unilateral ovariectomy. The data also indicate that the right ovary is more dependent on vagal influences for follicular activation than the left ovary.

Bilateral section of the pelvic parasympathetic nerves (pelvic-neurectomy) on day 5 of pseudopregnancy had no effect on the wet weight of ovaries, uteri, and/or cervices, but at day 9 serum progesterone was reduced to approximately half that of sham-operated animals. Collagen in the cervix was visualized with picrosirius red staining under polarization microscopy. Pelvic neurectomy decreased the birefringence of Type 1 collagen in the cervix to less than half that of sham operated animals. The decreased birefringence, an index of the organization of collagen fibers, is believed to be attributable to reduced progesterone levels. Alternatively, the pelvic nerve may directly influence mucopolysaccharides or collagenolytic enzymes in the cervix.

The effects of abdominal vagotomy at proestrus on ovarian weight and antral follicles greater than 150 µm diameter and on serum levels of gonadotropins and testosterone were assessed 24 and 48 h and 4 and 8 days after surgery. Serum levels of estradiol were assessed at 4 and 8 days. Vagotomy (1) increased ovarian weight at 48 h, decreased ovarian weight at 4 days, but had no effect by day 8. (2) Vagotomy increased healthy antral follicles 151–394 µm diameter at 24 and 48 h and increased atresia in this size range at 4 and 8 days. (3) Vagotomy decreased healthy follicles 151–394 µm at day 8. (4) Vagotomy decreased healthy follicles 395–570 µm at 24 h and decreased atretic follicles at 48 h. (5) Vagotomy decreased the largest (over 570 µm diameter) healthy follicles at 24 h and 8 days. (6) Vagotomy decreased basal serum LH levels at 48 h and 8 days. (In contrast, vagotomy increased FSH at 24 h). There was no effect on blood levels of estradiol and testosterone. These findings are discussed in relation to the hypothesis that the vagus nerve is a component of the hypothalamohy-pophyseal-ovarian axis.

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