AN AORTIC PROJECTION OF LUMBAR PARAVERTEBRAL SYMPATHETIC NEURONS IN THE BULLFROG

A population of sympathetic neurons which projects from paravertebral ganglia to the dorsal aorta was identified in the bullfrog based on it s electrophysiology and anatomy. The aorta is bilaterally supplied by about a dozen connective nerves arising from sympathetic ganglia 7-10. From compound action potentials, the majority of fibers can be identi fied as postganglionic axons belonging to both the B-and C-cell groups . Tracing experiments indicated that 95 +/- 21 (mean +/- SD) neurons p roject into each connective and that axons in connectives penetrate th e wall of the aorta where they break into small bundles. Staining whol emounts of the aorta for neuropeptide Y revealed a plexus of varicose axons which presumably arise from sympathetic C neurons. These observa tions imply that the aorta is sympathetically innervated by paraverteb ral C neurons.