SEGMENTAL RESTRICTION AND TARGET SPECIFICITY OF BULLFROG PREGANGLIONIC NEURONS THAT EXHIBIT GALANIN-LIKE IMMUNOREACTIVITY

These experiments were designed to examine the distribution of galanin -like peptide immunoreactivity (GAL-IR) in bullfrog sympathetic pregan glionic neurons and to identify the peripheral target organs affected by these neurons. Cells expressing GAL-IR were observed in the interme diolateral column of segments 7 and 8 only. Apparent GAL-IR innervatio n is present, but rare, in sympathetic chain ganglia. Double-labelling with retrogradely transported fast blue and galanin antiserum demonst rated that most GAL-IR neurons project via splanchnic nerves to innerv ate the adrenal gland, which receives a dense plexus of GAL-IR fibers surrounding chromaffin cells. The adrenal gland is also innervated by preganglionic neurons in segments 5 and 6 that do not express GAL-IR. Because nitric oxide is expressed in sympathoadrenal preganglionic neu rons in mammals (Anderson, C.R., Neurosci. Lett., 139 (1992) 280), we examined whether it is expressed in bullfrog preganglionic neurons. Ni cotinamide adenine dinucleotide phosphate-diaphorase positive neurons are present in bullfrog spinal grey at segments 5 through 8. These neu rons were not double-labelled with fast blue retrogradely transported from the sympathetic chain, celiac ganglion, or adrenal gland; nor wer e they double-labelled with GAL-antiserum. Thus nitric oxide is appare ntly not expressed in bullfrog sympathetic preganglionic neurons.