Origin of sensory and autonomic innervation of the rat temporomandibular joint: A retrograde axonal tracing study with the fluorescent dye fast blue

Previous studies that have used retrograde axonal tracers (horseradish pero xidase alone or conjugated with wheat germ agglutinin) have shown that the temporomandibular joint (TMJ) is supplied with nerve fibers originating mai nly from the trigeminal ganglion, in addition to other sensory and sympathe tic ganglia. The existence of nerve fibers in the TMJ originating from the trigeminal mesencephalic nucleus is unclear, and the possible innervation b y parasympathetic nerve fibers has not been determined. In the present work , the retrograde axonal tracer, fast blue, was used to elucidate these ques tions and re-evaluated the literature data. The tracer was deposited in the supradiscal articular space of the rat TMJ, and an extensive morphometric analysis was performed of the labeled perikaryal profiles located in sensor y and autonomic ganglia. This methodology permitted us to observe labeled s mall perikaryal profiles in the trigeminal ganglion, clustered mainly in th e posterior-lateral region of the dorsal, medial and ventral thirds of hori zontal sections, with some located in the anterior-lateral region of the ve ntral third. Sensory perikarya were also labeled in the dorsal root ganglia from C2 to C5. No labeled perikaryal profiles were found in the trigeminal mesencephalic nucleus. On the other hand, autonomic labeled perikaryal pro files were distributed in the sympathetic superior cervical and stellate ga nglia, and parasympathetic otic ganglion. Our results confirmed those of pr evious studies and also demonstrated that: (i) there is a distribution patt ern of labeled perikaryal profiles in the trigeminal ganglion; (ii) some pe rikaryal profiles located in the otic ganglion were labeled; and (iii) the trigeminal mesencephalic nucleus did not show any retrogradely labeled peri karyal profiles.