VIP and polycystic ovary syndrome: The increased population of VIP-IR nerve fibres within the medullar part of cystic ovaries was earlier observed following injection of DXM from the follicular phase of the estrous cycle (Kozłowska et al. 2008), and it has also been shown that the concentration of VIP rose markedly in the estradiol valerate (EV)-induced polycystic ovaries (Parra et al. 2007).