Topographic representation of lower and upper teeth within the trigeminal sensory nuclei of adult cat as demonstrated by the transganglionic transport of horseradish peroxidase

Abstract

Transganglionic transport of horseradish peroxidase-wheat germ agglutinin conjugate (HRP-WGA) entrapped in hypoallergenic polyacrylamide gel was used to study the patterns of termination of primary afferents that innervate the lower and upper tooth pulps within the trigeminal sensory nuclear complex (TSNC). HRP injections were made into the inferior and superior alveolar nerves in order to compare the central projections of the whole nerve with those from tooth pulps. In addition, the relationship between the distribution of the trigeminothalamic tract cells and the projection sites of the tooth pulp afferents was investigated by injecting HRP into the posterior ventral thalamus. HRP-labeled tooth pulp afferent fibers innervating the lower and upper teeth projected to the subnucleus dorsalis (Vpd) of pars principalis, the rostrodorsomedial part (Vo.r) and nucleus dorsomedialis (Vo.dm) of pars oralis, the medial regions of pars interpolaris, and laminae I, II, and V of pars caudalis. Terminal fields of the lower tooth pulp afferents formed a rostrocaudally running, uninterrupted column from the midlevel of Vpd to the caudal tip of caudalis. In contrast, the column of termination of upper tooth pulp afferents was discontinuous at the Vpd/Vo.r transition, and ended at the more rostral level of the caudalis than that of the lower tooth pulp afferents. The representation of the lower and upper teeth in the TSNC was organized in a somatotopic fashion which varied from one subdivision to the next, although terminal zones of the inferior and superior alveolar nerves overlapped within the Vo.r, Vo.dm, and dorsomedial part of rostral pars interpolaris. The lower and upper teeth were represented in the Vpd, Vo.r, Vo.dm, medial region of pars interpolaris, and laminae I, II, and V, in a ventrodorsal or caudorostral, dorsoventral, lateromedial, dorsoventral, and mediolateral or dorsomedial-ventrolateral sequence, respectively. The smaller, more focal terminal areas of the teeth contrasted sharply with more extensive terminal fields of the alveolar nerves. The HRP injections within the thalamus indicated that neurons in Vpd, the caudal pars interpolaris, and laminae I/V of caudalis, which are subdivisions of TSNC that receive pulpal projections, sent their axons to the ipsilateral and contralateral posterior ventral thalamus.(ABSTRACT TRUNCATED AT 400 WORDS)

Central projection of calcitonin gene-related peptide (CGRP)- and substance P (SP)-immunoreactive trigeminal primary neurons in the rat

“…This suggests that a considerable proportion of the trigeminal primary nociceptive projection, especially from the intraoral structures, is directed to the relay nuclei located in the rostral subdivisions of the BSTC. This idea is supported by the fact that a large proportion of central projection of presumed primary nociceptors innvervating the tooth pulp is directed to rostral subdivisions of the BSTC (Arvidsson and Gobel, 1981;Westrum et al, 1981;Marfurt and Turner, 1984;Shigenaga et al, 1986bShigenaga et al, , 1989Takemura et al, 1991;Sugimoto and Takemura, 1993).…”

“…In the former species, the PrV but not the Vo contains many projection neurons with ascending axons projecting to the contralateral nucleus ventralis posteromedialis (VPM) of the thalamus (Shigenaga et al, 1983(Shigenaga et al, , 1986b. Therefore, it may be that the principal relay nucleus involved in the intraoral nociception is the PrV in the cat.…”

Spontaneous Discharge and Peripherally Evoked Orofacial Responses of Trigemino–Thalamic Tract Neurons during Wakefulness and Sleep

“…Both electrophysiological (Sessle and Greenwood, 1976;Sessle and Hu, 1981;Azerad et al, 1982;Sunada et al, 1990;Ro and Capra, 1994) and anatomical labeling (Mizuno, 1970;Woda et al, 1977;Burton and Craig, 1979;Matsushita et al, 1982;Shigenaga et al, 1986;Matthews et al, 1987Matthews et al, , 1989) studies performed in acute anesthetized cats have demonstrated that the rostral trigeminal sensory nuclear complex (TSNC) comprising, respectively, the nucleus oralis and the main sensory nucleus, contains a high density of TGT neurons. Recently, we have shown that the tooth pulp-evoked activity of rostral TSNC neurons is suppressed specifically during the behavioral state of active (AS) or REM sleep .…”

Morphological differences between fast and slowly adapting lingual afferent terminations in the principal and oral nuclei in the cat

“…Regarding projections of primary afferents to the Vo.r and Vo.dm, we have reported that the lower and upper teeth are represented in a dorsoventral sequence (Shigenaga et al, 1986c), and projections from the anterior to posterior teeth are organized in a ventrolateral to dorsomedial sequence (Shigenaga et al, 1989b). The projections from lingual afferents in the Vo.r and Vo.dm are organized in a similar fashion to those of the lower teeth, but both terminal fields may overlap extensively.…”