NOVEL ANTIGENIC DETERMINANT EXPRESSED IN NEURONS OF THE DORSOLATERAL HYPOTHALAMUS IN RAT AND HUMAN

Previous studies have identified a group of cells in the dorsolateral hypothalamus that project to many different areas in the CNS, such as thalamus, diagonal band of Broca, basal ganglia, cerebral cortex, hippocampus, and olfactory bulb. Their role is presently unknown, but the cells have been reported to stain for an intriguing array of putative neurotransmitter-related substances, including alpha-melanocyte-stimulating hormone (alpha-MSH), melanin-concentrating hormone (MCH), human growth-hormone-releasing factor 1-37 (hGRF 1-37), corticotropin-releasing factor (CRF), metorphamide, and acetylcholine esterase. A monoclonal antibody produced in the present study, alpha-C11, stains both the cell bodies of this system in hypothalamus, with a punctate pattern, and varicose fibers in the various target areas. In double-label immunocytochemical experiments in rat DLH, alpha-C11 and MCH staining exactly overlaps. Concentrations of alpha-MSH and MCH high enough to completely block staining with the corresponding antisera had no effect on staining with alpha-C11. Similarly, CRF, hGRF 1-37, and metorphamide were unable to block alpha-C11-staining. The results suggest that the antigenic epitope for alpha-C11 is not contained in alpha-MSH, MCH, CRF, hGRF, or metorphamide, and thus, that alpha-C11 is detecting another antigen uniquely expressed in these neurons. The punctate appearance of staining in the hypothalamus and the concentration of staining in fiber varicosities suggests that the alpha-C11 epitope may be involved in synaptic function.