Injection of dye into neurones in rat and human post-mortem brain, in combination with acetylcholinesterase histochemistry: permanent preparations.

We describe a protocol for the intracellular injection of dye into neurones in thick sections of fixed, post-mortem rat and human brain tissue. To render the sections with the intracellularly injected neurones permanent, they are sectioned again, and the resulting subsections are either immunocytochemically treated or stained histochemically for acetylcholinesterase (AChE) activity. The resultant preparations can be stored at room temperature for prolonged periods. Background staining produced by accumulation of erythrocytes in blood vessels is greatly reduced or virtually eliminated by exposure of the sections to ultraviolet radiation prior to the intracellular injection. The pattern of AChE staining is not affected by this procedure. This ability to stain sections according to a histochemical AChE procedure after the intracellular injection of dyes into striatal neurons opens the possibility to study the relationship of neuronal dendritic trees with the striosome/matrix compartmental boundaries in post-mortem (human) brain tissue of Huntington's disease patients.