Fig. 1. Interneuron loss in the dentate gyrus of a pilocarpine-induced epileptic rat. Nissl-staining (a,b), GAD65 mRNA in situ hybridization (c, d), and somatostatin (e, f) and parvalbumin immunocytochemistry (g, h) demonstrate the loss of interneurons in adjacent sections from an epileptic rat (b, d, f,h) compared with a control (a,c, e, g). GAD65 mRNA expression appears more intense in surviving interneurons in the epileptic rat (d) compared with the control (c). The surviving somatostatin-immunoreactive somata and axons in the outer molecular layer (arrowheads) are labeled more intensely in the epileptic rat (f) compared with the control (e). Interneuron profiles (GAD65 mRNA-, somatostatin-, and parvalbumin-positive) were counted within the borders of the dentate gyrus that are demonstrated in a. Nissl-stained hilar neurons were counted only within the hilus (h). m, Molecular layer;g, granule cell layer; CA3, CA3 pyramidal cell layer. Scale bar, 250 μm.