Entorhinal and prepiriform cortices of the European hedgehog. A histochemical and densitometric study based on a comparison between Timm's sulphide silver method and the selenium method.

The Timm and selenium staining techniques, based on silver amplification of endogenous zinc, produce an electron-dense precipitate in boutons. The staining characteristics of the two methods were compared by examining two allocortical regions, prepiriform cortex and entorhinal cortex, in the brain of the European hedgehog. In the 3 layers of prepiriform cortex and the 6 layers of entorhinal cortex the methods revealed sublayers, which allows a precise delimitation of areas 28M, 28L, a short transition zone, and the prepiriform cortex. The lamination of the entorhinal cortex of the hedgehog is similar to that found in the rat, but appears less distinct. This may point to a lower degree of afferent organization. For light microscopical investigations, the selenium technique appears superior to Timm's method because it produces a more distinct zonation pattern.