The "accessory body" of Cajal in the neuronal nucleus. A light and electron microscopic approach.

The present light and electron microscopic study deals with the morphology and staining properties of two intranuclear inclusions - the "accessory body" of Cajal and the "coiled body"--in the supraoptic nuclei of adult rat hypothalamus, and supports the assumption that these structures represent the same intrinsic component of the neuronal nucleus. Consequently, we propose to term it "accessory body". The structure of this body was visualized by several different staining procedures: conventional electron microscopic techniques, a silver reaction, and the regressive EDTA staining for ribonucleoproteins. The silver-impregnation method employed here, which consists of a silver development sequence on hypothalamic tissue blocks prior to plastic embedding, permitted the study of supraoptic neurons at both light and electron microscopic levels. The nature and origin of "accessory bodies" are suggested and their possible functional role is briefly discussed.