We will continue our study of specific aspects of prenatalpituituary gland development in the rat. Our goal is to determine the role that different tissue interactions have in establishing lobe-specific biochemical difference between anterior and intermediate lobes of the pituitary gland, which have a common embryological origin (Rathke's pouch). We will continue to study differentiation of proopiomelancortin (POMC)-containing cells that are present in both anterior and intermediate lobes the pituitary but which differentiate at different times during development, process POMC to different end product hormone, and are differentially regulated in the adult. 1. We will continue to study aspects of fetal POMC processing. We will analyze processing of POMC-oligosaccharides in order to determine the intracellular compartment at which specific processing events occur during development and also examine the appearance of an adult-intermediate lobe specific processing gene by Northern blot analysis and in situ hybridization. 2. We will use the reverse-hemolytic plaque assay to examine the development of basal and stimulated secretory potential by POMC cells in both lobes and complement this analysis by using cDNA probes to the glucocoticoid receptor for in situ hybridization and Northern blot analysis. 3. We will examine the differentiative capacity of intermediate lobe POMC-producing cells in the presence or absence of infundibulum in vitro. 4. Finally, we will make and characterize antibodies to monoamine oxidase-A to complement our analysis of MAO-B and thus to provide insight into the regulation of prenatal pituitary function by MAO substrates such as serotonin noradrenaline, and dopamine.