Aspartate-immunoreactive primary sensory neurons in the mouse trigeminal ganglion

Aspartate-immunoreactivity (ir) was examined in the mouse trigeminal ganglion (TG). The ir was detected in 34% of TG neurons and their cell bodies were of various sizes (mean +/- S.D. = 1,234 +/- 543 microm(2)). A triple immunofluorescence method revealed the co-expression of aspartate with calcitonin gene-related peptide (CGRP) and parvalbumin; 22% and 14% of aspartate-immunoreactive (ir) neurons were also immunoreactive for CGRP and parvalbumin, respectively. The co-expression of aspartate with both CGRP and parvalbumin was very rare in the TG. By retrograde tracing method, half and 66% of TG neurons which innervate the vibrissa and palate, respectively, contained aspartate-ir. The co-expression of aspartate with CGRP was more common among palatal neurons (36%) compared to vibrissal neurons (22%). Aspartate-ir neurons which co-expressed parvalbumin-ir were numerous in the vibrissa (17%) but not in the palate (4%). These findings may suggest that the function of aspartate-containing TG neurons is correlated with their peripheral receptive fields.