Properties and projection sites of rostral trigeminal sensory complex units activated by noxious and non noxious stimuli in the rat

$52 PROPERTIES AND PROJECTION SITES OF ROSTRAL TRIGI94INAL SEN6! Po SORY COMPLEX UNITS ACTIVATED BY NOXIOUS AND NON NOXIOUS Monday ~ I M U L I IN THE RAT. J. Azerad, S. Laplante~ P. CheneauWand C. Nachon~ Laboratoire de Physiologie des Centres Nerveux, Facult@ de Chirurgie Dentaire, Universit6s Paris VI et Paris VII, France. The localization of termination of primary trigeminal afferents is better known at the caudal than at the rostral level of the trige~zinal sensory complex (TSC) in the rat. We began this work using the new technique of tmansganglionic transport of HRP using TMB reaction to map precisely these central projections on the classical delineations of the TSC. Various peripheral structures were injected with HRP : inferior and superior incisor dental pulp, periodontium, vibrissae and tongue. Afterwards tmit activity recordings were performed in Ketamine anaesthetized gallamine parallized rats under artificial respiration with classical extracellular recording and dye injection techniques. Noxious pinch and mechanical non noxious stimuli applied to orofacial structures were used to evoke responses in rostral TSC units, concurrently with electrical stimulation of dental incisor pulp, periodontium and transcutaneous activation following bilateral stimulation of Thalamus VPM and superior colliculus. All these precious criteria of activation were used to classify functionnally the trig~minal units in the aim to precise the anatc~tical and functional delineation between Principal sensory nucleus and oralis subnucleus in the Rat.

ONE CANINE PROJECTS TO ALL OF THE BRAIN STEM TRIGEMINAL I 62 Pc NUCLEI. L.E. Westruml, 2, R.C. Canfield*3, and 1 Monday T.A. O'Connor*l, Departments of iNeurological Surgery, 2Biological Structure, and 3Restorative Dentistry, University of Washington, Seattle, WA 98195, USA. Aim of Investisation: To determine the precise sites of representation in the brain stem for specific teeth and their periodontal structures. Methods: Horseradish peroxidase (HRP) was implanted in the pulpal chamber of either maxillary or mandibular canines unilaterally in adult cats. After 1-3 days the tetramethylbenzidine (TMB) technique was used to prepare the tissue for study with the light microscope. Projection patterns were mapped in dark field from serial sections using a camera lucida attachment. Results: i.) Both procedures gave HRP positive cells and fibers in the ipsilateral trigeminal ganglia and fibers in the peripheral nerve and central root. 2.) HRP positive fibers from each tooth are distributed widely to each ipsilateral subdivision of the trigeminal nuclear complex with "terminals" often occurring in clusters. 3.) The heaviest terminations are in the dorsal main sensory nucleus, adjacent pars oralis, pars interpolaris and rostral pars caudalis near obex. 4.) The terminal fields from the mandibular canine are similar to those of the maxillary rostrally in main sensory nucleus and pars oralis but more restricted than the maxillary in pars interpolaris. In pars caudalis the maxillary canine has a broader projection to substantia gelatinosa with more deep clusters, while the mandibular is mainly confined to dorsal areas. Conclusions: The findings show some differences between maxillary and mandibular canines in the more caudal subnuclei but a much more extensive ipsilateral CNS representation than previously reported for a single tooth. (Supported by NIH Grants DE 04942, NS 09678, and NS 04053. LEW is an affiliate of the CDMRC, University of Washington, Seattle, Washington.)