Immunoreactiivty for nNOS, SP and HO2 as markers for inhibitory and excitatory nerve cell bodies and fibers. Panels A-C. Normal immunoreactivity for nNOS in control (A) and case 1 (B). nNOS immunoreactivity was markedly decreased in case 2 (C). Panels D-F. Substance P expression was normal in control (D), case 1 (E), and case 2 (F). Panels G-I. Heme Oxygenase II (HO-2) immunoreactivity was normal in control (G) and case 1 (H). Sections from Case 2 (I) showed a loss of HO-2 immunoreactivity which together with the decrease in nNOS immunoreactivty suggests a loss of inhibitory input ot smooth muscle. Scale bar 100 μm. Circular muscle (CM), longitudinal muscle (LM).