Abstract
Fertility decreases during aging in females, but the exact pathophysiological mechanisms in the hypothalamus are not clarified yet. Anti-Müllerian hormone (AMH) is a member of transforming growth factor (TGF)-β superfamily, and its important roles in ovaries are studied. However, recent studies have unveiled extragonadal functions. AMH stimulates gonadotropin-releasing hormone (GnRH) neurons via AMH receptor type 2 (AMHR2). Moreover, we recently reported that 75–85% of cell bodies and fibers of GnRH neurons are positive for both AMH and AMHR2 in the preoptic area (POA), arcuate nucleus (ARC), and the internal and external zones of the median eminence (ME). Plasma AMH concentrations can predict the fertility of adult female animals, suggesting important roles of AMH and AMHR2 in infertility during aging. Therefore, we hypothesized that both protein amounts would differ in the anterior hypothalamus (containing the POA) and posterior hypothalamus (containing the ARC and ME) between young post-pubertal heifers and old cows. We obtained brain samples from healthy post-pubertal wagyu Japanese Black heifers (25.9 ± 0.6 months of age; n=5; luteal phase) and old wagyu Japanese Black cows (89.7 ± 20.3 months of age; 5.2 ± 0.5 parity; n=5). We used a previously reported method of western blotting (Kereilwe et al., 2018, 2019) using the same anti-AMH rabbit polyclonal antibody and the same anti-bovine AMHR2 antibody. Western blot analysis showed lower (P<0.05) expressions of AMH and AMHR2 in the posterior hypothalamus, but not in the anterior hypothalamus, of old Japanese Black cows compared to young heifers. Therefore, AMH and AMHR2 were decreased in the posterior hypothalami of old cows.
