Abstract
Some of the paravertebral sympathetic ganglia of the dog contain relatively large amounts of dopamine, which we have suggested previously is localized in dopaminergic neurones. However, the possibility exists that intraganglionic chromaffin-like cells may also be a source of dopamine. In order to resolve this question, we have examined the distribution of chromaffin-like cells in dog paravertebral ganglia (T 7-S 2) using formaldehyde-induced fluorescence of catecholamines and immunohistochemical localization of dopa decarboxylase, dopamine β-hydroxylase and phenylethanolamine N-methyltransferase. The results have been compared with levels of the different endogenous catecholamines in equivalent ganglia. Clusters of between 20 and several thousand chromaffin-like cells were randomly present in ganglia at all levels of the chain, and were most common in the more caudal segments (L 4 or below); but many ganglia contained no cells. About 24,000 chromaffin-like cells were found in 18 ganglia from six animals which were stained for dopa decarboxylase and dopamine β-hydroxylase. In 16 of these ganglia, all of the 17,000 cells present contained both enzymes, indicating that they could synthesize noradrenaline. In the remaining two ganglia, 500 out of 7000 cells contained dopa decarboxylase, and therefore were capable of synthesizing dopamine, but appeared to lack the dopamine β-hydroxylase necessary to convert this to noradrenaline. Five ganglia from three other dogs were stained for dopamine β-hydroxylase and phenylethanolamine N-methyltransferase. A further 2600 cells were found in these ganglia and both enzymes were present in all of the cells, indicating that they could all synthesize adrenaline. Biochemical estimates of the various catecholamines snowed that ganglia containing appreciable amounts of adrenaline had similar distributions to those containing chromaffin-like cells in the same animals. High concentrations of adrenaline were often correlated with high concentrations of noradrenaline but were not correlated with high concentrations of dopamine. It is concluded that paravertebral chromaffin-like cells in the dog store adrenaline, and also perhaps noradrenaline, but not dopamine. The high concentrations of dopamine found in certain ganglia cannot therefore be attributed to the presence of these cells. The erratic distribution of chromaffin-like cells suggests that they are unlikely to fulfil any general role in modulation of ganglionic transmission.
Published Version
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