Identification of a novel neuronophagic cell in the partially denervated rat neurohypophysis

Abstract

The objective of this study was to identify neuronophagic cells in the partially denervated neurohypophysis. This was accomplished by using a phagocytosis‐dependent labeling technique to visualize the incorporation of labeled axonal debris within neuronophagic cells in the neurohypophysis following unilateral transection of the hypothalamo‐neurohypophysial tract (HNT). Stereotaxic application of the biotin and rhodamine conjugated dextran amine Mini Ruby into the magnocellular neurons of the supraoptic nucleus led to conspicuous and stable labeling of the HNT. Following unilateral lesion of the HNT, we observed small rhodamine labeled granules within s100beta immunoreactive pituicytes, and also within immunophenotypically identified perivascular cells expressing the p75 low affinity neurotrophin receptor, the C3bi compliment receptor, and ciliary neurotrophic factor. At the ultrastructural level, we observed homogeneous labeling of magnocellular neurons and neurosecretory axons with Mini Ruby. In the partially denervated neurohypophysis, labeled axons were found to be enveloped by pituicyte processes as well as within the pituicyte cytoplasm. These results indicate that the anterograde degeneration induced by partial denervation of the rat neurohypophysis stimulates neuronophagia by both perivascular cells and pituicytes. This study was supported by COBRE 2P20RR017699‐06Grant Funding SourceCOBRE 2P20RR017699‐06