NEUROTROPHIN SENSITIVITY OF PREVERTEBRAL AND PARAVERTEBRAL RAT SYMPATHETIC AUTONOMIC GANGLIA

Prevertebral and paravertebral sympathetic autonomic ganglia respond d ifferently to a large number of experimental and clinical insults. The selective involvement of subpopulations of sympathetic neurons may re flect differences in their response to neurotrophic substances. To tes t this hypothesis, we investigated the response of prevertebral and pa ravertebral rat sympathetic ganglia to selected neurotrophic substance s in vivo and in vitro and identified the ganglionic distribution of n eurons expressing high affinity neurotrophin receptor mRNAs. Dissociat ed cultures of embryonic prevertebral and paravertebral ganglionic neu rons showed comparable responses to NGF deprivation and only small dif ferences in their response to rescue with other trophic substances. In situ hybridization studies of adult rat sympathetic ganglia using pro bes specific for the high-affinity neurotrophin receptor transcripts t rks A, B, and C demonstrated that neurons in both prevertebral and par avertebral sympathetic ganglia express predominantly trkA receptors in vivo. In addition, increased tyrosine hydroxylase (TOH) activity was induced only by doses of neurotrophic substances that activate trkA an d showed only small differences between neonatal prevertebral and para vertebral ganglia. Although small differences in the sensitivity of pr e-and paravertebral sympathetic neurons to various neurotrophins have been identified in our studies, they are unlikely, in isolation, to ex plain major differences in the sensitivity of these ganglia to neuropa thologic processes.