Immunocytochemical demonstration of LH-RH, somatostatin, and ACTH-like peptide in osmium-postfixed, resin-embedded median eminence.

In guinea pig median eminences that were fixed with a glutaraldehyde paraformaldehyde mixtures, postfixed with osmium tetroxide, and embedded in araldite, immunocytochemical stainings for luteinizing hormone-releasing hormone (LH-RH), somatostatin, and alpha 17-39 ACTH have been obtained on semithin sections. These positive reactions were obtained after araldite was removed with sodium methoxide and after treatment with hydrogen peroxide. These data suggest that osmium tetraoxide postfixation can be used for the detection of low molecular weight peptides such as LH-RH, somatostatin, and ACTH-like-peptides not only in the median eminence but also in the hypothalamus.