Potassium permanganate can mark the site of microdialysis in brain sections

Microdialysis is a technique used to study the extracellular environment or to deliver minute quantities of drugs into the central nervous system and other tissues in physiological experiments. It may have an expanding role i n clinical studies. It can be used to study the microenvironment or to stud y the systemic effects of extremely localized pharmacological interventions , without interpretation of the results being confounded by systemic distri bution of circulating drug. Proper interpretation of experimental results, however, depends on precise histological localization of the site of microd ialysis or microinjection. This paper describes a simple method using potas sium permanganate in 1% filtered aqueous solution to mark the site of exper imental microdialysis or microinjection in brain tissue. Potassium permanga nate reacts with brain tissue to produce insoluble, tar-like organic mangan ese dioxide reaction products that make a more visible mark than staining w ith either 5% neutral red or 5% fast green. Subsequent tissue processing an d histological staining with cresyl violet or hematoxylin, eosin, and Luxol fast blue did not obscure the mark.