AXONAL-TRANSPORT OF FLUORESCENT CARBOCYANINE DYES ALLOWS MAPPING OF PERIPHERAL-NERVE TERRITORIES IN GINGIVA

SENSORY INNERVATION OF GINGIVAL TISSUE can cause neurogenic inflammati on that depends on the extent of the branching area of the peripheral nerve fibers, We designed the present study to determine whether singl e trigeminal axons branch to both the buccal and palatal gingiva of ma xillary molars of adult rats, Accumulation via retrograde transport of DiI (red) or DiA (green) fluorescent carbocyanine dyes in neurons of trigeminal ganglia was evaluated 7 days after applying one dye to the buccal sulcus and the other to the palatal sulcus. Both dyes were abso rbed through the junctional epithelium, and the two sites each labeled similar numbers and sizes of neurons in the lateral zone of the maxil lary division (44% from buccal and 46% from palatal gingiva). Double-l abeled neurons had the same size (32.5 +/- 6.70 mu m, mean circumferen ce +/- S.D.) and location as single-labeled neurons, and they were 9% of the total. This study shows that exogenous dyes can diffuse into mu cosa and thereby allow in vivo mapping of sensory nerve branching patt erns to several intact tissues per animal. We found that 9% of the lab eled cells extended to both the buccal and palatal gingiva. Thus, infl ammation that spreads from one gingival region to the other could have a neurogenic mechanism involving trigeminal sensory neurons that exte nd their peripheral branches to innervate both buccal and palatal ging iva of adult rat molars.