The effects of vagotomy on compensatory ovarian hypertrophy and follicular activation after unilateral ovariectomy

Abstract

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.

In vivo and in vitro study of the function of the left and right bovine ovaries

“…[35]. The evidence obtained from pharmacologic or surgical denervation suggests that ovarian innervation participates in the regulation of ovarian functions [36] and vagal innervations can differentially affect follicular numbers in the left and right ovaries in rats [37]. Another possibility is the existence of some kind of vascularization information between the ovaries, as was proposed previously [38].…”

Dorsal rhizotomy does not alter rat estrous cycles or ovarian compensatory responses

“…These remaining intact spinal and vagal afferents may have been adequate to mediate afferent neural ovarian responses. Previous workers have shown that the vagus Burden and Lawrence 1978;Gerendai and Nemeskeri 1983;Burden et al 1986;Chavez et al 1987); spinal cord hem• (Gerendai and Halasz 1978) and medial basal hypothalamus deafferentation (Gerendai 1980;Nance et al 1983Nance et al , 1984Fukuda et al 1984) have suggested that in addition to hormonal factors, a pure neural component is involved in compensatory ovarian hypertrophy after unilateral ovariectomy. The pathways involved in such a link would be multisynaptic.…”

“…On day 15 all animals were decapitated, and the remaining ovary was cleaned, weighed, and fixed in neutral buffered formalin. A time duration up to day 15 was chosen because previous studies (Burden and Lawrence 1977;Burden et al 1986) have demonstrated that this period is appropriate for other neurally modulated alterations in follicular activation and compensatory ovarian hypertrophy after unilateral ovariectomy.…”

“…However, Aron et al (1948) noted the rapidity of compensatory ovarian responses following unilateral ovariectomy and suggested that nerves were also involved in this phenomenon. Subsequently, several workers presented evidence for participation of vagal (Burden and Lawrence 1977;Gerendai and Nemeskeri 1983;Burden et al 1983Burden et al , 1986Chavez et al 1987) or adrenergic ) components in compensatory ovarian hypertrophy. Deafferentation of the medial basal hypothalamus (Gerendai 1980;Nance et al 1983Nance et al , 1984 or spinal cord hemitransection (Gerendai and Halasz 1978) also altered this hypertrophy.…”

“…Effect of unilateral section of dorsal roots Tlz-L2 at estrus on antral follicular development (mean number of foliicles,+ SEM) 15 days after surgery Number in parenthesis is number of animals b Significantly (P<0.05) different from day i by paired t-test nerves help mediate ovarian responses subsequent to unilateral ovariectomy(Burden and Lawrence 1977;Gerendai and Nemeskeri 1983;Burden et al 1986; Cha- vez et al 1987). Thus it is possible that the results recorded in the present study were a consequence of inadequate ovarian deafferentation.…”