Location of feline trigeminal ganglion cells innervating maxillary canine teeth: a horseradish peroxidase analysis

196 ~;TOMATOLOGY Degenerative changes in primary trigeminal axons and in neurons in nucleus caudalis following tooth pulp extirpations in the cat. -- S. Gobel and J.M. Binck, Brain Res., 132 (1977) 347--354 The removal of infected tooth pulps results in destruction of the receptor endings of small myelinated and unmyelinated axons innervating the pulp chambers of teeth. Subsequent filling of the chamber with inert materials precludes any regeneration of these endings. This paper demonstrates with EM techniques that tooth pulp extirpations in cat result in degenerative changes in the central terminations of these primary trigeminal neurons and i:~ the neurons tb .~y synapse on in the marginal (layer I ) a n d substantia gelatinosa (layers I! and #:II) layers of nucleus caudalis. The degenerating primary endings in layer I show a blackened axoplasm and are rapidly phagocytosed by glial cells. Their rapid degeneration parallels the disappearance of anmyelinated axons from the spinal V tract and suggests that they are the +.erminals of these unmyelinated axons. Primary endings in layers II and III, on the other hand, degenerate in situ over a longer time period, gradually losing their synaptic vesicles and synaptic connections. Their gradual degeneration parallels the protracted degeneration of primary myelinated axons in the spinal V tract, suggesting they are connected to myelinated axons. In summary, these experiments indicate major primary afferent and transsynaptic degenerative changes following tooth pulp removal. It is possible that such changes play ~ role in oral-facial pathological pain conditions ill humans. Location of feline tfigeminal ganglion cells innervating maxillary canine teeth: a horserad:~sh peroxidase analysis. -- K.V. Anderson and H.S. Rosing, Exp. Neurol., 57 (1977) 302--306 This study exarnired the ~omatotopical organization of cell bodies in the trigeminal ganglion connected to per,:pheralafferents innervating maxillary canine teeth in cat. Horseradish peroxidase (HRP) wa~ injected into exposed too~;h pulps on one s~de and its transport to ganglion cellswas examined 24-72 h later. H R P granules were observed in cells of ipsilateraland contralaterai ganglia. Mos;~ cells containing H R P were of small to medium size (less than 4,3 /~m). Label~cl cells were distributed throughout the maxillary portion of the ganglia ,~.,ithgreater numbers found h~ the ventral regions. N o H R P cells were observed in control animals. Th~s report of transmedian innervation of feline canine teeth is of considerable interestand is consistent wi.~!~other reports usi~igdifferent anatomical and physiological methods. The o1~gin of h~ipulses recorded ~orn dentinal cavities in the tooth of the cat.--G, i-hegers~am, Acta physiol, scand., 97 (1976) 121--128 Evidence is presented that single unit discharges recorded from dentinal cavities in teeth erigfna~e from nerve fibers in the tooth pulp. Voltage differences measured betwee~, two cavities in cat canine teeth appear to originate