Fig. 2.

Computer-enhanced autoradiograms of coronal sacral spinal cord sections from wild-type (+/+) and homozygous (−/−) A_2A knock-out mice. The sections were taken were the S4 segment according to the rat atlas of Paxinos and Watson (1986). μ receptors were labeled with [³H]DAMGO (4 nm), δ receptors with [³H]deltorphin-I (7 nm), κ receptors with [³H]CI-977 (2.5 nm), ORL1 receptors with [³H]nociceptin (0.4 nm), and A_2A receptors with [³H]CGS21680 (10 nm). Nonspecific binding (NSB), shown in the far right column, was determined in the presence of naloxone (1 μm for μ and κ and 10 μm for δ), unlabeled nociceptin (100 μmfor ORL1), or 5′-N-ethylcarboxamidoadenosine (20 μm for A_2A). The color bar shows a pseudocolor interpretation of the relative density of the black and white film image calibrated in femtomoles per milligram of tissue. Sections from +/+ and −/− spinal cords were processed in parallel.