Pituitary adenylate cyclase-activating polypeptide innervation of the mudpuppy cardiac ganglion

The presence and potential origin of the neuropeptide pituitary adenylate c yclase-activating polypeptide (PACAP) was determined in cardiac ganglia of the mudpuppy, Necturus maculosus. Although PACAP has been implicated in the regulation of cardiac function in several mammalian species, the presence of this peptide in the autonomic nervous system (ANS) of other species is u nclear. Thus, this study is the first to characterize this highly conserved peptide in the ANS of a non-mammalian species. PACAP-immunoreactivity was observed in nerve fibers throughout the mudpuppy cardiac ganglia and often was co-localized with the sensory neuropeptides substance P and calcitonin gene-related peptide. Removal of all extrinsic inputs to the ganglia by org an culture eliminated PACAP-immunoreactivity in the cardiac ganglia, wherea s bilateral vagotomies only partially reduced PACAP-labeling. PACAP-immunor eactive neurons were observed in both high thoracic dorsal root ganglia and in vagal sensory ganglia. While no PACAP-positive neurons were observed in caudal medulla brainstem regions, PACAP-containing herve fibers were found in the region of the nucleus solitarius. These results suggest that, in th e mudpuppy, PACAP is found primarily in visceral afferent fibers, originati ng from cells in either the dorsal root ganglia or vagal sensory ganglia. B ased on their anatomic localization, these afferent fibers may function to transmit important sensory information to cardiovascular centers in the bra in as well as serving as local reflex inputs to modulate postganglionic par asympathetic output within the cardiac ganglion itself. (C) 2000 Elsevier S cience B.V. All rights reserved.