The proposed research project is designed to establish the functional significance of the rostral zone of the pars intermedia, to determine the possible relationship between the pars intermedia and adrenal zona glomerulosa (aldosterone production) and to define the hypothalamic nucleus or nuclei and their axon terminals involved in the control of activity of the pars intermedia. To attain these objectives, ultrastructural qualitative morphometric and immunocytochemical (ACTH) as well as physiologic data (plasma aldosterone and corticosterone) will be obtained under a variety of experimetal conditions: (l) in rats bearing electrolytic lesions in hypothalami nuclei, especially the suprachiasmatic and rostral arcuate nuclei, (2) in animals with the pars intermedia rostral zone grafted into various hypothalamic nuclei (especially suprachiasmatic and rostral arcuate nuclei) and subjected to an intense neurogenic stress (sound), (3) in sodium deficient hypophysectomized rats receiving extracts of pars intermedia and (4) in sodium deficient rats.