The effects of neuropeptide Y (NPY; 0, 10, 100 and 1000. ng/mL) on the expression of PCNA, bax and p53 proteins were examined by immunocytochemistry in porcine luteinized granulosa cells. NPY inhibited proliferation as well as promoted apoptosis and accumulation of p53 in the cells. This is the first report to demonstrate the direct action of NPY on ovarian cell proliferation and apoptosis. The results of the study suggest that the effect is mediated by transcription factor p53. © 2015 Society for Biology of Reproduction & the Institute of Animal Reproduction and Food Research of Polish Academy of Sciences in Olsztyn.