Immunoreactive Adrenocorticotropin in Rat Brain: a Neuroanatomical Study Using Antiserum Generated Against Synthetic ACTH

In this study an antiserum generated against synthetic ACTH1--39 is used to provide a neuroanatomical map of ACTH-immunoreactivity in rat brain. Groups of ACTH-immunoreactive cell bodies were located in the basal hypothalamus, extending from the retrochiasmatic region to the mammillary nuclei. The fiber distribution indicates a broad innervation of structures in the hypothalamus, which include the medial preoptic region; bed nucleus of the anterior commissure and stria terminalis; perifornical region; periventricular stratum; and paraventricular, dorsomedial, arcuate, and mammillary nuclei. Fibers from the hypothalamus reach the amygdaloid nuclei directly in two separate bundles. A large dorsal ACTH-immunoreactive bundle emerges from the anterior hypothalamic region, distributes to the periventricular thalamic nuclei, and continues more posteriorly to the midbrain periaquaductal gray. It is speculated that the cell bodies in the ventral tuberal region of the hypothalamus are responsible for the vast innervation of fibers to the forebrain, diencephalon, and brainstem.