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 α‐melanocyte‐stimulating hormone (αMSH), 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, αCl1, 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, αCl1 and MCH staining exactly overlaps. Concentrations of αMSH and MCH high enough to completely block staining with the corresponding antisera had no effect on staining with αC11. Similarly, CRF, hGRF 1–37, and metorphamide were unable to block αCl1 staining. The results suggest that the antigenic epitope for αCl1 is not contained in αMSH, MCH, CRF, hGRF, or metorphamide, and thus, that αCl1 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 αCl1 epitope may be involved in synaptic function.