Sympathetic ganglia are innervated by neuropeptide-containing fibers originating from pre- and postganglionic sympathetic neurons, dorsal root ganglion neurons, and in some cases, myenteric neurons. In the present report receptor autoradiography was used to determine whether sympathetic ganglia express receptor binding sites for several of these neuropeptides including bombesin, calcitonin gene-related peptide-α, cholecystokinin, galanin, neurokinin A, somatostatin, substance P, and vasoactive intestinal polypeptide. The sympathetic ganglia examined included the rat and rabbit superior cervical ganglia and the rabbit superior mesenteric ganglion. High levels of receptor binding sites for cholecystokinin, galanin, somatostatin, substance P, and vasoactive intestinal polypeptide were observed in all sympathetic ganglia examined, although only discrete neuronal populations within each ganglion appeared to express receptor binding sites for any particular neuropeptide. These data suggest that discrete populations of postganglionic sympathetic neurons may be regulated by neuropeptides released from pre- and postganglionic sympathetic neurons, dorsal root ganglion neurons, and myenteric neurons.
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