ENKEPHALINS OCCUR AND COLOCALIZE WITH SUBSTANCE-P IN HUMAN TRIGEMINALGANGLION NEURONS

IMMUNOHISTOCHEMICAL evidence is provided for (i) the occurrence of a p rimary sensory neuronal population immunoreactive to methionine- and l eucine-enkephalin (EK) in the human trigeminal ganglion; (ii) colocali zation of EK and substance P (SP) in a subpopulation of ganglion neuro nes and in nerve fibres and terminal-like structures in the human trig eminal spinal nucleus. The results obtained indicate that part of the EK-positive innervation of the spinal nucleus may be of ganglionic ori gin and raise the possibility that EK and SP are costored in and corel eased from primary afferent terminals, thus adding to the complexity o f the sites and ways of interaction between these neuropeptides in the processing of sensory information.