Differential distribution of nerve terminals immunoreactive for substance P and cholecystokinin in the sympathetic preganglionic cell column of the filefish Stephanolepis cirrhifer

Immunoreactivity for substance P and cholecystokinin-8 was examined in the nerve fibers in the central autonomic nucleus, a cell column for sympatheti c preganglionic neurons, in the filefish Stephanolepis cirrhifer. Substance P-immunoreactive fibers were distributed throughout the entire rostrocauda l extent, but were more abundant in the caudal part of the column, where su bstance P-immunoreactive varicosities sometimes made contacts with the symp athetic preganglionic neurons. Cholecystokinin-8-immunoreactive fibers were found almost entirely in the rostral part of the column, where a dense net work of varicosities was in close apposition to a considerable number of th e sympathetic preganglionic neurons. Double labeling immunohistochemistry s howed that substance P fibers and cholecystokin-8 fibers were entirely diff erent, and distinct from serotonin-immunoreactive fibers. By using immunoel ectron microscopy, synaptic specialization was sometimes observed between t he dendrites of preganglionic neurons and varicosities immunoreactive for s ubstance P and cholecystokinin-8. Substance P- and cholecystokinin-8 fibers were seen from the descending trigeminal tract, through the dorsolateral f uniculus and the ventral portion of the dorsal horn, to the central autonom ic nucleus. After colchicine treatment, substance P-immunoreactive perikary a were found in the cranial and spinal sensory ganglia. These results sugge st that the sympathetic preganglionic neurons of the filefish receive inner vation by substance P fibers and cholecystokinin fibers, and that the forme r might be of primary sensory origin. Topographical distribution of cholecy stokinin-8-immunoreactive terminals in the central autonomic nucleus along the rostrocaudal extent might underlie the differential regulation of sympa thetic activity via a distinct population of sympathetic preganglionic neur ons. (C) 2000 Wiley-Liss, Inc.