Time-course of post-denervation changes in calcitonin gene-related peptide and substance P immunoreactive nerve fibres in superior cervical ganglion in rat

In rat sympathetic ganglia decentralization by preganglionic denervation leads to intraganglionic sprouting of adrenergic nerve and also in an intraganglionic increase of peptidergic fibres immunoreactive (IR) for substance P (SP) and calcitonin gene-related peptide. We explored the time-course of the post-denervation changes in intraganglionic nerve fibres immunoreactive for calcitonin gene-related peptide and substance p in superior cervical ganglia of normal rats and of rats at intervals from 2 days to 70 days following preganglionic denervation with prevented reinnervation. This study has indicated that many if not all fibres of the networks arise, in two phases, by sprouting from small bundles of similarly immunoreactive nerve fibres which traverse the normal ganglion, entering or leaving it at many points. They survive preganglionic denervation and are thus probably sensory. It is suggested that activity in such new sensory collateral branches may contribute to the low levels of ganglionic activation observable in the autonomic failure of multiple system atrophy in man.