A number of electrophysiological studies have been devoted to the functional organization of trigeminal nucleus oralis (TNO) with only a very few anatomical analyses directed toward an understanding of the structural substrates underlying the electrophysiological events. TNO has been implicated in the reception, central processing and modification and the transmission of neural information related to oral-facial nociceptive (pain) and mechanoreceptive (tactile) stimuli and it is perceived as being involved in numerous chronic pain states such as trigeminal neuralgia (tic douloureux). TNO is a major target of primary trigeminal neurons which innervate the tooth pulp where it is generally considered that pain is the only sensation that can be elicited in man. The overall objectives of my studies are to delineate the synaptic circuitry in TNO in order to understand and explain how nociceptive and mechanoreceptive information transmitted from the oral-facial region by primary trigeminal neurons is processed before being relayed to other centers in the brain. This proposed project is concerned with the synaptic connections of the sensory root of the trigeminal nerve and the morphology of the neurons which comprise TNO. These studies employ light (LM) and electron (EM) microscopy, the Golgi method and the intra-axonal anterograde horseradish peroxidase (HRP) labeling technique.
The specific aims of the proposed research are: (1) to demonstrate the distribution of primary trigeminal afferent axons to TNO of the adult rat; (2) to examine the morphological features of individual HRP-filled terminal axonal arbors of primary trigeminal afferent axons in TNO with LM and then evaluate their cytology and synaptic relations with EM; and (3) to identify the neuronal cell types in TNO and assess the overall morphology and distribution of their axons and dendrites. The knowledge gained from these studies will provide an essential anatomical framework for understanding the synaptic circuitries through which TNO processes oral-facial nociceptive and mechanoreceptive information under normal and pathological circumstances. Such an understanding, in light of concurrent pharmacological advances in drug therapy, should contribute to the successful treatment of trigeminal related chronic pain states which affect the face and oral cavity.

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Research Project (R01)
Project #
5R01DE006725-03
Application #
3220223
Study Section
Oral Biology and Medicine Study Section (OBM)
Project Start
1984-01-01
Project End
1986-12-31
Budget Start
1986-01-01
Budget End
1986-12-31
Support Year
3
Fiscal Year
1986
Total Cost
Indirect Cost
Name
Michigan State University
Department
Type
Schools of Osteopathy
DUNS #
193247145
City
East Lansing
State
MI
Country
United States
Zip Code
48824
Phelan, K D; Falls, W M (1991) A comparison of the distribution and morphology of thalamic, cerebellar and spinal projection neurons in rat trigeminal nucleus interpolaris. Neuroscience 40:497-511
Phelan, K D; Falls, W M (1991) The spinotrigeminal pathway and its spatial relationship to the origin of trigeminospinal projections in the rat. Neuroscience 40:477-96
Falls, W M; Moore, B J; Schneider, M T (1990) Fine structural characteristics and synaptic connections of trigeminocerebellar projection neurons in rat trigeminal nucleus oralis. Somatosens Mot Res 7:1-18
Phelan, K D; Falls, W M (1989) An analysis of the cyto- and myeloarchitectonic organization of trigeminal nucleus interpolaris in the rat. Somatosens Mot Res 6:333-66
Phelan, K D; Falls, W M (1989) The interstitial system of the spinal trigeminal tract in the rat: anatomical evidence for morphological and functional heterogeneity. Somatosens Mot Res 6:367-99
Falls, W M (1988) Synaptic organization of primary axons in trigeminal nucleus oralis. J Electron Microsc Tech 10:213-27
Falls, W M; Alban, M M (1986) Morphological features of identified trigeminocerebellar projection neurons in the border zone of rat trigeminal nucleus oralis. Somatosens Res 4:1-12
Falls, W M (1986) Morphology and synaptic connections of unmyelinated primary axons in the border zone of rat trigeminal nucleus oralis. Neurosci Lett 70:342-7
Falls, W M (1986) Morphology and synaptic connections of myelinated primary axons in the ventrolateral region of rat trigeminal nucleus oralis. J Comp Neurol 244:96-110
Falls, W M; Alban, M M (1986) Morphology and synaptic connections of small myelinated primary trigeminal axons arborizing among neurons in the border zone of rat trigeminal nucleus oralis. Somatosens Res 4:97-110

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