The neuroendocrine and neuropeptide profile of toxically treated animals is being developed as a potential tool in the systematic evaluation of neurotoxicity. These assays are performed by radio-immune techniques involving the iodination of purified antibodies. Levels of prolactin, ACTH, TSH, and steroid hormones are determined in serum while endorphins, enkephalins, neurotensin, and substance P are assayed in homogenates of brain regions. Toxicants that have been tested include acrylamide, kepone, and monosodium glutamate. The neonatal administration of this latter compound has been found to significantly depress plasma testosterone levels of treated male rats. Kepone-exposed rats showed no significant alterations of testosterone or prolactin.