ULTRASTRUCTURAL-LOCALIZATION OF NEUROTENSIN IMMUNOREACTIVITY IN THE STELLATE GANGLION OF THE CAT

The morphological features and cellular relationships of neurotensin-c ontaining axon terminals were studied at light and electron microscopi c levels in the cat stellate ganglion using peroxidase and immunogold immunocytochemistry. By light microscopy, neurotensin immunoreactivity was detected within thin varicose fibres distributed throughout the g anglion. Immunoreactive fibres were no longer apparent following chron ic deafferentation of the ganglion indicating that they were of extrin sic origin. Ultrastructural analysis of peroxidase immunostained mater ial confirmed the presence of neurotensin immunoreactivity within a su bpopulation of axonal varicosities which made synaptic contacts with t he dendrites of ganglion cells. Within labelled varicosities neurotens in immunoreactivity was found by both immunoperoxidase and immunogold methods to be concentrated within large dense core vesicles 80-120 nm in diameter. These large dense core vesicles were characteristically d istant from the active zone, in keeping with a possible extrasynaptic release of the peptide.