GALANIN EXPRESSION INCREASES IN ADULT-RAT SYMPATHETIC NEURONS AFTER AXOTOMY

Changes in neuropeptide expression occur in sensory, motor, and sympat hetic neurons following axotomy. The particular pattern of peptide cha nges that occurs varies among the three cell types. We have studied th e regulation in the rat superior cervical ganglion of the expression o f galanin, a peptide previously shown to increase in axotomized sensor y and motor neurons. While normally only an occasional neuron exhibiti ng galanin-like immunoreactivity is found in this ganglion, at two day s after transection of the postganglionic internal and external caroti d nerves, immunostaining can be observed in many neurons throughout th e ganglion. Similar changes are found when ganglia are placed in organ culture for two days. The distribution of immunostained neurons after section of only one of the postganglionic trunks suggests that change s in galanin-like immunoreactivity occur only within neurons whose axo ns are transected. None the less, even when both nerve trunks are tran sected, only about half of the neurons in the ganglion exhibit galanin -like immunoreactivity, indicating that only a proportion of the axoto mized neurons exhibit a detectable response. The few immunostained neu rons seen after section of the cervical sympathetic trunk may also rep resent axotomized neurons. Galanin-like immunoreactivity extracted fro m the ganglion co-chromatographs with authentic galanin, and the level of this immunoreactivity increases dramatically after axotomy and exp lantation, and modestly after decentralization. These same manipulatio ns produce parallel increases in the level of galanin messenger RNA.