MELANOTROPIC PEPTIDES - PRESENCE IN BRAIN OF NORMAL AND HYPOPHYSECTOMIZED RATS, AND SUBCELLULARLY LOCALIZED IN SYNAPTOSOMES

A major and several minor tricholoroacetic acid (TCA) soluble, bioassayable melanotropic peptides, as well as bioreactive and immunoreactive α‐MSH have been found in the hypothalamus, olfactory bulb and cerebral cortex of normal and hypophysectomized rats. By employing subcellular fractionation procedures it was demonstrated that α‐MSH and the major TCA soluble melanotropic peptide (MMPB) were localized in synaptosomes and were released by hypoosmotic shock. The analysis of MMPB by electrophoretic and chromatographic procedures reveals that it is not ACTH4−10, ACTH1−10, ACTH1−24, NAcACTH1−10 or α‐MSH. MMPB was found to cross‐react with an antiserum specific for the Lys‐Pro‐Val NH2 sequence in α‐MSH, indicating that this C‐terminal sequence of α‐MSH may be present in its structure. MMPB was also shown to differ electrophoretically from the two major TCA soluble melanotropic peptides found in the neurointermediate lobe of the pituitary. In view of their synaptosomal localizations MMPB and α‐MSH may play a role in synaptic function in the nervous system. Copyright © 1979 Alan R. Liss, Inc.