CHEMICAL SYMPATHECTOMY AND POSTGANGLIONIC NERVE TRANSECTION PRODUCE SIMILAR INCREASES IN GALANIN AND VIP MESSENGER-RNA BUT DIFFER IN THEIR EFFECTS ON PEPTIDE CONTENT

Large changes in neuronal gene expression occur in adult peripheral ne urons after axonal transection. In the rat superior cervical ganglion, for example, neurons that do not normally express vasoactive intestin al peptide (VIP) or galanin do so after postganglionic nerve transecti on, These effects of axotomy could result from a number of aspects of the surgical procedure, To test the idea that the important variable m ight be the disconnection of axotomized neuronal cell bodies from thei r target tissues, we examined the effects of producing such a disconne ction by means of the compound 6-hydroxydopamine (6-OHDA), a neurotoxi n that causes degeneration of sympathetic varicosities and avoids many of the complications of surgery, Two days after 6-OHDA treatment, VIP and galanin immunoreactivities had increased two- and 40-fold. respec tively. Nevertheless, these increases were substantially smaller than the 30- and 300-fold changes seen after surgical axotomy. When express ion of VIP and galanin was examined at the mRNA level, however, compar able increases Here found after either procedure. The results indicate that chemical destruction of sympathetic varicosities produces an equ ivalent signal for increasing VIP and galanin mRNA as does axonal tran section. The differences in the neuropeptide levels achieved suggests that peptide expression after nerve transection is regulated both at t he mRNA and protein levels. (C) 1996 John Wiley & Sons, Inc.