Plasticity in the phenotypic expression of catecholamines and vasoactive intestinal peptide in adult rat superior cervical and stellate ganglia afterlong-term hypoxia in vivo

Sympathetic ganglia in the adult rat contain various populations of nerve c ells which demonstrate plasticity with respect to their transmitter phenoty pe. The plasticity of the neuronal cell bodies and of the small intensely f luorescent cells in the superior cervical and stellate ganglia in response to hypoxia in vivo (10% O-2 for seven days) was assessed by studying the ex pression of catecholamines and vasoactive intestinal peptide. The levels of norepinephrine, dopamine, 3,4-dihydroxyphenylacetic acid and vasoactive in testinal peptide immunoreactivity were determined. In addition, the density of the immunohistochemical staining of cells for tyrosine hydroxylase and vasoactive intestinal peptide was evaluated. In the intact superior cervica l ganglion, hypoxia increased the dopamine level as well as the density of small intensely fluorescent cells immunolabelled for tyrosine hydroxylase a nd vasoactive intestinal peptide. In the axotomized ganglion, hypoxia elici ted a twofold rise in the level of the vasoactive intestinal peptide as wel l as enhancing the density of neuronal cell bodies immunostained for this p eptide. Thus, the effect of hypoxia on the expression of vasoactive intesti nal peptide expression in neurons was dependent on neural interactions. In the intact stellate ganglion, hypoxia alone induced a 1.5-fold increase in the density of neuronal cell bodies immunostained for vasoactive intestinal peptide. Thus, ganglia-specific factors appeared to play a role in determi ning changes in neuronal phenotype in response to hypoxia. The present study provides evidence for the involvement of dopamine and vas oactive intestinal peptide in ganglionic responses to long-term hypoxia as well as for differential responses by the two ganglionic cell populations, i.e. neuronal cell bodies and small intensely fluorescent cells. Changes in the expression of the vasoactive intestinal peptide during long-term hypox ia may be of energetic, trophic and/or synaptic significance. Hypoxia may b e considered to be a vasoactive intestinal peptide-inducing factor in sympa thetic ganglia. (C) 1999 IBRO. Published by Elsevier Science Ltd.