CLATHRIN LIGHT-CHAIN AND SYNAPTOTAGMIN-I IN RAT SYMPATHETIC NEURONS

Clathrin light chain (clathrin LC) and synaptotagmin I in sympathetic neurons in rat superior cervical ganglia (SCG) were studied using immu nofluorescence and confocal microscopy. The distributions of clathrin LC and synaptotagmin I were compared with that of tyrosine hydroxylase (TH) and neuropeptide Y (NPY) in double label experiments. The influe nce of preganglionic regulation on the expression of clathrin LC and s ynaptotagmin I in post-ganglionic adrenergic neurons was investigated after cutting the cervical sympathetic trunk. In SCGs and irides of co ntrol animals, the clathrin LC- and synaptotagmin-I-positive structure s were present in a granular pattern in nerve fibers and varicose term inals. In principal neurons, the two proteins were present in a perinu clear network (the Golgi complex). After decentralization, the synapto tagmin-I- and clathrin LC-positive granules normally present in pregan glionic nerve terminals outlining the neuronal somata were no longer o bserved on day 1, but reappeared, and were increased above control in number and intensity, in axon bundles in the ganglia, on day 3 and up to day 28 post-decentralization. In irides, the fluorescence intensity and density of clathrin LC- and synaptotagmin-I-positive nerve termin als in the dilator plate, were semi-quantified using the confocal micr oscopy software. It was found that both proteins increased shortly aft er decentralization. Immunoblot data confirmed the immunohistochemical /confocal microscopy observations. Fast axonal transport of clathrin L C- and synaptotagmin I in preganglionic sympathetic neurons was demons trated in crush-operated cervical sympathetic trunk. Both proteins rap idly accumulated proximally as well as distally to the crush, demonstr ating fast anterograde and retrograde axonal transport (recycling). Th us, clathrin LC and synaptotagmin I are normally present in pre- as we ll as post-ganglionic sympathetic neurons. The colocalization of clath rin LC with synaptotagmin I in the Golgi complex of the adrenergic neu rons may imply that clathrin participates in the synthesis/sorting of the fast transported materials in these neurons. Possible explanations for the increase of the two proteins after decentralization are discu ssed.