The immunohistochemical distribution of neuropeptide Y in lumbar pre- and paravertebral sympathetic ganglia of the guinea pig.

Neuropeptide Y (NPY)- like immunoreactive nerve cell bodies and nerve fibres have been studied in normal and colchicine-treated ganglia of the caudal lumbar sympathetic chain (LSC) and the inferior mesenteric ganglion (IMG) of the guinea pig. The great majority of noradrenergic ganglion cells in the LSC (defined as containing tyrosine hydroxylase immunoreactivity), but less than 20% of those in the IMG, were NPY-positive. These proportions correspond well to the proportions of neurones that have been found to discharge phasically in electrophysiological experiments on the same ganglia. As noradrenergic terminals innervating blood vessels contain NPY, the data are consistent with the idea that phasic discharge is a characteristic of vasoconstrictor neurones.