Precautions in the application of immunohistochemical techniques to tissues of the pig hypothalamo-neurohypophysial system.

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Abstract
Immunohistochemical procedures were used to localize neurophysin in the hypothalamo-neurohypophysial axis of the domestic pig. The topographical distribution of neurophysin as revealed by the immunofluorescence "sandwich" technique was similar to that found when either the immunoglobulin-peroxidase bridge method or the peroxidase-labeled gamma-globulin technique was employed. However, application of the peroxidase-anti-peroxidase (PAP) complex procedure resulted in nonspecific staining of the magnocellular structures. This phenomenon was attributed to the action of PAP on the tissue and after screening a number of other vertebrate species was found to be unique to the pig. Minimal nonspecific binding of the PAP could be achieved either by reducing the reaction time of PAP to 5 min or, by the addition of 1% (v/v) normal serum to all reagents and wash solution. That the PAP-binding protein is a component of the hypothalamo-neurohypophysial axons is discussed.