The neuraliy depressant amino acid taurine and related metabolites were tested for their ability to alter prolactin (PRL) secretion in conscious, unrestrained male rats. The intraventricular infusion oftaurine (0.2 and 2.0 μmol) elicited a significant increase in PRL secretion. Hypotaurine (0.2 and 2.0 μmol), cysteic acid (2.0 μmol), mannitol (2.0 μmol) and 0.9% saline were ineffective in altering PRL secretion. When infused directly into the pituitary of conscious, unrestrained male rats none of the substances tested stimulated PRL secretion. Taurine (50.0 μmol) was similarly ineffective in stimulating PRL secretion when an in vitro pituitary preparation was used. These studies indicate that taurine is capable of stimulating PRL secretion in the male rat. This effect appears to be mediated centrally, presumably at the hypothal