Immunoreactive ACTH/beta-endorphin neurons in the tubero-infundibular hypothalamus of rats

In the preinfundibular portion of male rat hypothalamus, the arcuate-median eminence region was examined after staining with anti-porcine ACTH 1-39 serum. In several cases, anti-beta-endorphin serum was also employed. Both sera stain the same cell bodies. The cell bodies of the immunoreactive neurons are scattered in the subependymal layer, arcuate nucleus and lateral tuberal region. Fibers originating from these cell bodies are distributed extensively throughout these regions. They make synaptic contacts on immunonegative fibers in the arcuate nuclei, or terminate directly in the perivascular space in the internal layer of the median eminence. The findings suggest that the ACTH/beta-endorphin neuronal system may serve neuronally and humorally as an intrahypothalamic constituent of the hypothalamic pituitary regulation system.