The use of sodium sulphide-fixed brain tissue for immunocytochemical staining of activated microglia and reactive astrocytes.

The use of sodium sulphide-perfused material for the immunocytochemical demonstration of microglia and astrocytes is described. An intracerebroventricular injection of kainic acid (KA) was used to induce neuronal degeneration and subsequent axonal sprouting in the hippocampus. Animals under deep anaesthesia were killed by perfusion with either 4% paraformaldehyde alone or with 1% sodium sulphide followed by 4% paraformaldehyde solution. Microglial cells were identified with OX-42, a monoclonal antibody towards CR3 complement receptors, and astrocytes with a polyclonal antibody to glial fibrillary acidic protein (GFAP). The present study reveals a marked enhancement in the immunoreactivity of activated microglial cells in sodium sulphide perfused tissues compared to those observed in tissues fixed in paraformaldehyde alone. GFAP immunoreactivity of the astrocytes was not compromised by the use of sodium sulphide. The results clearly show the suitability of sodium sulphide perfused tissues for immunocytochemical procedures and should provide a useful tool for investigation of the role of neuroglial cells in axonal sprouting.