Relationship of the central ACTH-immunoreactive opiocortin system to the supraoptic and paraventricular nuclei of the hypothalamus of the rat.

ACTH-immunoreactive (ir) fibers of the central opiocortin system are present in high density in the mid-portion of the paraventricular nucleus (PVN). ACTH-ir fibers, however, do not appear to directly contact oxytocin-ir vasopressin-ir, containing perikarya or axons of vasopressinergic neurons. Magnocellular neurons located more anteriorly and posteriorly in the PVN as well as those located laterally have few ACTH-ir fibers associated with them. No ACTH-ir fibers are present in the supraoptic nucleus.