Fig. 1. Preparation of cortex–striatum–substantia nigra cultures (triple cultures). A, B, Cortical (cx), striatal (cp), and nigral (sn) tissue regions dissected from transversal rat brains at PND 0–2 indicated by black lines [E22; plate 7 and 19 taken from Altman and Bayer (1995)]. C, Arrangement of the dissected tissues during culturing.D–H, Quantitative analysis of striatal TH-ir fiber densities. D, A CLSM picture at high magnification taken 8 μm below the striatal surface. First, an estimation of the background intensity is achieved by placing aline onto regions with no TH-ir fibers present (E, background). Then, straight lines are placed at 0, 45, 90, and 135° (measure, only 0° shown). E,G, Typical pixel intensities over distance for abackground and a measure line, respectively. F, The background distribution from which a threshold was chosen at mean + 4 × SD (filled arrows in F, H; broken lines in E, G). H, This threshold used to determine the number of pixels above threshold (PAT) in the pixel intensity distribution obtained from the measure (gray area).