Dystrophins in neurohypophysial lobe of normal and dehydrated rats: immunolocalization and biochemical characterization

DYSTROPHIN, utrophin and dystroglycan are present not only in muscle but al so in brain. In muscle, they link the extracellular matrix to the cytoskele ton. Their function in brain is not understood. Here we show their presence in the hypothalamo-neurohypophysial system which secretes the neurohormone s oxytocin and vasopressin. Using immunocytochemistry, we showed that dystr ophins are present in the neurohypophysis of control rats. After water depr ivation, immunoreactivity dramatically decreased and appeared in axonal swe llings in the hypothalamic tract. Dystrophin immunostaining can be ascribed to dystrophin and/or utrophin as well as the DMD (Duchenne Muscular Dystro phy) gene short products Dp140 and Dp71 as revealed by Western immunoblots of synaptosomes isolated from neurohypophyses of control rats. In synaptoso mes isolated from rats under water deprivation, the immunoreactivity entire ly disappeared. Further biochemichal characterization of isolated neurosecr etory granules (NSG) showed that Dp140 and Dp71 are enriched in the NSG sto red in the swellings of the neurohypophysis whereas the NSG of the nerve en dings are devoid of these proteins. In addition we observed that the presen ce of beta-dystroglycan and actin correlates with the presence of dystrophi ns. Our data favor a direct implication of the dystrophins and/or utrophin, dystroglycan and actin in the neurosecretory processes of the hypothalamon eurohypophysial system. NeuroReport 9: 3583-3587 (C) 1998 Lippincott Willia ms & Wilkins.