Suprachiasmatic nucleus and vagus nerve trigger preovulatory LH and ovulation

Abstract

The suprachiasmatic nucleus (SCN) regulates the activity of several peripheral organs through a parasympathetic-sympathetic pathway. Previously, we demonstrated that atropine (ATR) microinjection in the right SCN of rats during proestrus blocks ovulation. In the present study, we analysed whether the vagus nerve is one of the neural pathways by which the SCN regulates ovulation. For this, CIIZ-V strain cyclic rats on the day of proestrus were microinjected with a saline solution (Vh) or ATR in the right or left SCN, which was followed by ventral laparotomy or ipsilateral vagotomy to the microinjection side. Some animal groups were sacrificed 1) on the same day of the surgery to measure oestradiol, progesterone and luteinizing hormone (LH) levels or 2) at 24 hours after surgery to evaluate ovulation. The left vagotomy in rats microinjected with ATR in the left SCN did not modify ovulation. In rats with ATR microinjection in the right SCN, the right vagotomy increased the levels of steroids and LH on the proestrus and ovulatory response. The present results suggest that the right vagus nerve plays a role in the multisynaptic pathways of communication between the SCN and the ovaries and indicate that such neural information participates in the regulation of the oestradiol and progesterone surge, which triggers the preovulatory peak of LH and determines ovulation.

Dysregulated mammalian estrus cycle rescued by timed activation of VIP neurons in the circadian pacemaker and late afternoon light exposure

“…ChR2 activation at CT10 rescued proestrus frequency in half of the experimental cohort (VIP-Cre x ChR2, 4 females out of 8), compared to one VIP-Cre x ChR2 animal in the control group (no excitation) (Figure S9B). While we verified fiber localization using post hoc LiGS histology and activation of SCN VIP neurons by c-Fos labeling under the fiber (Figure S9C), it is possible that the variable results were due to differences in fiber localization affecting the distribution of the light relative to the core of the SCN, heterogeneous distribution of neuronal subpopulations, or asymmetric connectivity of the SCN to the ovary ( 41 ).…”

“…Note that other VIPergic populations outside the SCN might also signal to GnRH neurons through VPAC2 ( 56 ). In addition, VIP could also act through other paths, including local suprachiasmatic stimulation of AVP neurons, which are known to regulate Kiss1 neurons, or via peripheral stimulation of the ovary ( 12, 41 ). Consistent with the former, we observed estrous cycle disruption by knockdown of KISS1R in MPA GnRH neurons.…”

Organization of the Subdiaphragmatic Vagus Nerve and Its Connection with the Celiac Plexus and the Ovaries in the Female Rat

“…These include the extrahypothalamic areas (NST, DMV, nucleus ambiguous, area postrema, cell group A7, Barrington nucleus, locus coeruleus, and periaqueductal gray matter) and the dorsal hypothalamus [17], which have neurophysiological roles in ovarian function [18,41,42]. Thus, the VN plays a role in the multisynaptic pathways of communication between the CNS and the ovaries, especially in the synthesis of estradiol and progesterone [43].…”