Co-localization of retrogradely transported wheat germ agglutinin and the putative neurotransmitter substance P within trigeminal ganglion cells projecting to cat middle cerebral artery.

Neurons containing both wheat germ agglutinin (WGA) and substance P (SP) immunoreactivities were found in the ophthalamic division of the ipsilateral trigeminal ganglia following application of the axonally transported lectin WGA to cat middle cerebral artery. Immunohistochemistry was accomplished by staining for WGA and SP on adjacent sections by using the chromogen diaminobenzidine, or by staining on a single section with sequential application of WGA and SP antisera using the chromogens diaminobenzidine and 4-chloro-1-naphthol, respectively. These observations confirm the results of trigeminal lesion studies indicating that trigeminovascular projections to the middle cerebral artery in the cat contain the neurotransmitter SP. In addition, other neurotransmitters may be present in this pathway since less than 50% of WGA-labeled cells contained SP.