A variety of drugs can alter the secretion of prolactin (PRL) by the pituitary gland in most animals. Secretion of prolactin is predominantly, under negative control of hypothalamus, and in this respect, it is unique among the pituitary hormones. This study was undertaken to evaluate the crop-sac diameterical response to ouabain treated Uromastix pituitary suspension. 0.1 ml suspension of ouabain treated Uromastix pituitary gave a minimum diametric crop-sac response of 0.85 cm and a maximum of 0.95 cm. Data indicates that oubain promotes the secretion of prolactin inhibiting hormone (PRIH), and produces hypoprolactinemia.