MK at the optimal concentration of 10 ng/ml promoted the survival of mouse mesencephalic neurons in culture as demonstrated by the increased number of microtubule-associated protein-2 (MAP2) immunostaining-positive and tyrosine hydroxylase immunostaining-positive neurons and an elevated uptake of radiolabeled dopamine.; To examine the neurite-guiding activity of MK, rat embryonic brain cells (embryonic days 17-18) were cultured on plates coated with purified MK in a grid pattern. The cells attached to and extended their neurites along the substrate pattern.