[Demonstration of glutamate in primary sensory trigeminal neurons innervating dental pulp in rats].

Primary sensory trigeminal neurons supplying the dental pulp of incisors in rats were labelled by retrograde axonal transport. Using an auto-metallographic intensification procedure, 48 hrs. after injection of wheat-germ colloidal gold in the pulp, gold particles were detected in the cytoplasm of the neurons as black granulations. Glutamate was found in 45-60% of the neurons by submitting ganglion slices to an anti-glutamate immuno-serum revealed by immunocytochemistry. Among the neurons supplying the dental pulp of incisors by their peripheral process, 70% are Glu+, 30% Glu-. These observations suggest that the population of neurons supplying the dental pulp is not functionally homogeneous and that Glu- neurons use a different neurotransmitter. The coexistence of Glu+ and Glu- neurons could also indicate that glutamate expression is modulated during the life of these neurons.