Accelerated regeneration of central catecholamine fibers in cat occipital cortex: effects of substance P.

Remarkably fast regeneration of central noradrenaline (NA) fibers was recently observed in the 6-hydroxydopamine (6-OHDA)-perfused occipital cortex. In the present study, we found that this reinnervation by NA fibers was further accelerated by substance P (SP) perfused into the fourth ventricle but not by SP directly perfused into the cortex. The site of SP's action is therefore most likely located in the soma-dendritic area of NA cells in the locus coeruleus (LC). The regeneration-stimulating effect of SP seems to be mediated by a process specific to SP, since the similar treatment with bethanechol in place of SP was ineffective.