The central projection of masticatory afferent fibers to the trigeminal sensory nuclear complex and upper cervical spinal cord

Retrograde and anterograde transport of horseradish peroxidase-wheat germ agglutinin (HRP-WGA) conjugate was used to study the organization of primary afferent neurons innervating the masticatory muscles. HRP applied to the nerves of jaw-closing muscles--the deep temporal (DT), masseter (Ma), and medial pterygoid (MP)--labeled cells in the trigeminal ganglion and the mesencephalic trigeminal nucleus (Vmes), whereas HRP applied to nerves of the jaw-opening muscles--anterior digastric (AD) and mylohyoid (My)--labeled cells only in the trigeminal ganglion. Cell bodies innervating the jaw-closing muscles were found with greater frequency in the intermediate region of the mandibular subdivision, while somata supplying the jaw-opening muscles were predominant posterolaterally. The distribution of their somatic sizes was unimodal and limited to a subpopulation of smaller cells. Projections of the muscle afferents of ganglionic origin to the trigeminal sensory nuclear complex (TSNC) were confined primarily to the caudal half of pars interpolaris (Vi), and the medullary and upper cervical dorsal horns. In the Vi, Ma, MP, AD, and My nerves terminated in the lateral-most part of the nucleus with an extensive overlap in projections, save for the DT nerve, which projected to the interstitial nucleus or paratrigeminal nucleus. In the medullary and upper cervical dorsal horns, the main terminal fields of individual branches were confined to laminae I/V, but the density of the terminals in lamina V was very sparse. The rostrocaudal extent of the terminal field in lamina I differed among the muscle afferents of origin, whereas in the mediolateral or dorsoventral axis, a remarkable overlap in projections was noted between or among muscle afferents. The terminals of DT afferents were most broadly extended from the rostral level of the pars caudalis to the C3 segment, whereas the MP nerve showed limited projection to the middle one-third of the pars caudalis. Terminal fields of the Ma, AD, and My nerves appeared in the caudal two-thirds of the pars caudalis including the first two cervical segments, the caudal half of the pars caudalis and the C1 segment, and in the caudal part of the pars caudalis including the rostral C1 segment, respectively. This rostrocaudal arrangement in the projections of muscle nerves, which corresponds to the anteroposterior length of the muscles and their positions, indicates that representation of the masticatory muscles in lamina I reflects an onion-skin organization. These results suggest that primary muscle afferent neurons of ganglionic origin primarily mediate muscle pain.(ABSTRACT TRUNCATED AT 400 WORDS)     

The Central Distribution of Primary Afferents from the External Eyelids, Conjunctiva, and Cornea in the Rabbit, Studied Using WGA-HRP and B-HRP as Transganglionic Tracers

We have analyzed the afferent limb of the eyeblink and nictitating membrane response of the rabbit by tracing the central distribution of primary afferents from the periorbital skin, conjunctiva, and cornea using horseradish peroxidase agglutinated to wheat germ (WGA-HRP) or conjugated to choleragenoid (B-HRP) as transganglionic tracers. Afferents in the periorbital skin and conjunctiva distribute most heavily to pars caudalis of the spinal trigeminal nucleus (Vc) and to the dorsal horn of spinal segment C1 (dhC1). These afferents terminate predominantly in laminae IIo and IIi and more weakly to the adjacent laminae I and III. There are much weaker projections to spinal segment C2, rostral Vc, and adjacent reticular formation (laminae IV and V) and to the lateral part of pars interpolaris of the spinal trigeminal nucleus (Vi). No conjunctival primary afferents were seen in the rostral divisions of the trigeminal system. Weak afferent inputs from the periorbital skin are present ventrally in pars oralis of the spinal trigeminal nucleus (Vo) and in the principal trigeminal nucleus (Vp). Corneal afferents distribute most densely in the ventral part of Vi and in islands of neuropil within the trigeminal tract at the level of Vi. They also project to caudal Vc and the adjacent dhC1 in laminae I, II, and III. There are sparse projections to the ventral and dorsal parts of Vp and to the ventral part of Vo. Reticular areas adjacent to ventral Vi also receive a few corneal afferents. WGA-HRP- and B-HRP-labeled terminals were distributed similarly in most areas, but lamina I of Vc received terminals labeled with WGA-HRP and Vp and Vo received cutaneous afferents labeled with B-HRP only. Since all subdivisions of the trigeminal system receive periocular and corneal afferent inputs, we suggest that all these subdivisions may be involved in reflex eyeblinks in the rabbit.     

Afferent fibers in the hypoglossal nerve: a horseradish peroxidase study in the cat

The existence of afferent fibers in the cat hypoglossal nerve was studied by transganglionic transport of horseradish peroxidase (HRP). Injections of wheat germ agglutinin-conjugated HRP (WGA-HRP) into the hypoglossal nerve resulted in some retrograde labeling of cell bodies within the superior ganglia of the ipsilateral glossopharyngeal and vagal nerves. A few labeled cell bodies were also present ipsilaterally within the inferior ganglion of the vagal nerve and the spinal ganglion of the C1 segment. Some of the labeled glossopharyngeal and vagal fibers reached the nucleus of the solitary tract by crossing the dorsal portion of the spinal trigeminal tract. Others distributed to the spinal trigeminal nucleus pars interpolaris and to the ventrolateral part of the medial cuneate nucleus by descending through the dorsal portion of the spinal trigeminal tract. In the spinal cord these descending fibers, intermingling with labeled dorsal root fibers, distributed to laminae I, IV-V and VII-VIII of the C1 and C2 segments. Additional HRP experiments revealed that the fibers in laminae VII-VIII originate mainly from dorsal root of the C1 segment.     

Ascending and descending internuclear projections within the trigeminal sensory nuclear complex

The cells of origin of ascending and descending internuclear pathways in the trigeminal sensory nuclear complex were studied by the method of retrograde transport of horseradish peroxidase in the cat. The cells of origin of the ascending internuclear pathways are distributed in all laminae of the caudal part of the spinal trigeminal nucleus (Vc) except for lamina II and the caudal regions of the pars interpolaris of the spinal trigeminal nucleus (Vi). The cells arising from the Vc project to all rostral trigeminal nuclei except the caudal Vi and dorsal part of the principal trigeminal nucleus (Vpd), and neurons of the caudal Vi project to the dorsomedial (Vo.dm) and rostrodorsomedial (Vo.r) divisions of the spinal trigeminal nucleus and the ventral part of the principal trigeminal nucleus (Vpv), although the main ascending fibers from the Vc arise from laminae III-V and project to the rostral Vi and pars oralis. By contrast, the cells of origin of the descending internuclear pathways are distributed in all trigeminal nuclei, with chain-like connections between the neighboring nuclei, while the caudal regions of the Vi and laminae I-II do not receive any descending projections. The main ascending fibers from the paratrigeminal nucleus (or interstitial nucleus) at the caudal level of the Vi project to the parabrachial nucleus. These findings indicate that the internuclear pathways are differentially organized between the ascending and descending projections, and suggest that the internuclear trigeminal connections have a smaller influence on the trigeminothalamic tract cells in the Vpd, caudal Vi, and lamina I.     

Primary afferent projections from the upper respiratory tract in the muskrat.

The central projections of the ethmoidal, glossopharyngeal, and superior laryngeal nerves were determined in the muskrat by use of the transganglionic transport of a mixture of horseradish peroxidase (HRP) and wheat germ agglutinin (WGA)-HRP. The ethmoidal nerve projected to discrete areas in all subdivisions of the ipsilateral trigeminal sensory complex. Reaction product was focused in ventromedial portions of the principal nucleus, subnucleus oralis, and subnucleus interpolaris. The subnucleus oralis also contained sparse reaction product in its dorsomedial part. Projections were dense to ventrolateral parts of laminae I and II of the rostral medullary dorsal horn, with sparser projections to lamina V. Label in laminae I and V extended into the cervical dorsal horn. A few labeled fibers were followed to the contralateral dorsal horn. The interstitial neuropil of the ventral paratrigeminal nucleus was densely labeled. Extratrigeminal primary afferent projections in ethmoidal nerve cases involved the K?lliker-Fuse nucleus and ventrolateral part of the parabrachial nucleus, the reticular formation surrounding the rostral ambiguous complex, and the dorsal reticular formation of the closed medulla. Retrograde labeling in the brain was observed in only the mesencephalic trigeminal nucleus in these cases. The cervical trunk of the glossopharyngeal and superior laryngeal nerves also projected to the trigeminal sensory complex, but almost exclusively to its caudal parts. These nerves terminated in the dorsal and ventral paratrigeminal nuclei as well as lamina I of the medullary and cervical dorsal horns. Lamina V received sparse projections. The glossopharyngeal and superior laryngeal nerves projected to the ipsilateral solitary complex at all levels extending from the caudal facial nucleus to the cervical spinal cord. At the level of the obex, these nerves projected densely to ipsilateral areas ventral and ventromedial to the solitary tract. Additional ipsilateral projections were observed along the dorsolateral border of the solitary complex. Near the obex and caudally, the commissural area was labeled bilaterally. Labeled fibers from the solitary tract projected into the caudal reticular formation bilaterally, especially when the cervical trunk of the glossopharyngeal nerve received tracer. Labeled fibers descending further in the solitary tract gradually shifted toward the base of the cervical dorsal horn. The labeled fibers left the solitary tract and entered the spinal trigeminal tract at these levels. Retrogradely labeled cells were observed in the ambiguous complex, especially rostrally, and in the rostral dorsal vagal nucleus after application of HRP and WGA-HRP to either the glossopharyngeal or superior laryngeal nerves. In glossopharyngeal nerve cases, retrogradely labeled neurons also were seen in the inferior salivatory nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)     

Oral and facial representation in the trigeminal principal and rostral spinal nuclei of the cat

Transganglionic transport of horseradish peroxidase (HRP) was used to study the patterns of termination of somatic afferent fibers innervating oral and facial structures within the principal nucleus (Vp), nucleus oralis (Vo), and nucleus interpolaris (Vi). The primary trigeminal afferent fibers that innervate the oral cavity supplied by the pterygopalatine, superior alveolar, lingual, buccal, and inferior alveolar branches, as well as the facial skin supplied by the frontal, corneal, zygomatic, infraorbital, auriculotemporal, mylohyoid, and mental branches, were traced in this experiment. The results show that trigeminal afferent nerves that innervate the oral cavity project mainly to the principal nucleus, the rostrodorsomedial part (Vo.r) and dorsomedial division (Vo.dm) of pars oralis, and the dorsomedial region of pars interpolaris, while an extensive overlap of projections is found in the Vo.r, Vo.dm, and rostral Vi. The central processes of fibers innervating the anterior face (i.e., mental, infraorbital, and frontal nerves) terminate in the ventral division of principalis (Vpv), caudal region pars oralis (Vo.c), and ventrolateral Vi, with the largest numbers of terminals being found in the Vpv and Vi. In contrast, the central projection patterns of the corneal, zygomatic, mylohyoid, and auriculotemporal afferents are different from those of other afferent nerves examined, and present a discrete projection to the trigeminal sensory nuclear complex (TSNC). The corneal, mylohyoid, and auriculotemporal afferents mainly project to the restricted regions of principalis and caudal Vi, while zygomatic afferent nerve fibers project to the caudal third of pars interpolaris. The typical somatotopic organization with the face of the mouth open inverted is represented in the rostrocaudal midlevels of the Vpv and caudal pars interpolaris. The Vpd receives topographical projection from primary afferent nerves that innervate the oral structure only, while this projection was organized in a complicated manner. The relationship between the functional segregation and the cytoarchitectonic differentiation of the TSNC is discussed, particularly with respect to this somatotopic organization, combined with the characteristics of projecting cells in the TSNC.     

Morphology of central terminations of intra-axonally stained, low-threshold mechanoreceptive primary afferent fibers from oral mucosa and periodontium in the rat

Horseradish peroxidase (HRP) was injected intra-axonally into functionally identified primary afferent fibers within the rat spinal trigeminal tract in order to study the morphology of their central terminations. They were physiologically determined to be large, myelinated afferent fibers from periodontium or oral mucosa by means of electrical and mechanical stimulation of their receptive fields. Twenty-eight axons that innervated the periodontium of incisors and 21 axons that innervated the oral mucosa were stained for distances of 2-5 mm from the injection sites at the levels of the main sensory nucleus (Vms), spinal trigeminal nucleus and rostral cervical spinal cord. The collaterals of these primary afferent fibers formed terminal arbors in the medial or dorsomedial part of the Vms, and the oral and interpolar spinal trigeminal nuclei (Vo and Vi). In the caudal spinal trigeminal nucleus (Vc), the collaterals of one half of the periodontium afferent fibers terminated mainly in lamina V at the rostral and middle levels of Vc. On the other hand, the collaterals of the other half of the periodontium afferent fibers terminated mainly in lamina IV at the rostral level of Vc, and rostrally these terminal areas shifted to the most medial part of Vi. The collaterals of mucosa afferent fibers terminated in lamina V at the rostral level of Vc, and these terminal areas shifted gradually to laminae III and IV as the parent axons traveled more caudally. These shifts were staggered rostrocaudally according to the rostrocaudal locations of the receptive fields. The density of collaterals of periodontium afferent fibers in Vi was significantly larger than that of mucosa afferent fibers. The average size of the varicosities of periodontium afferent fibers was significantly larger than those of mucosa afferent fibers in Vo, Vi and Vc. The average number of varicosities belonging to single collaterals of slowly-adapting periodontium afferent fibers in Vi were significantly larger than those in Vo. In Vi, the average number of varicosities of single collaterals of slowly-adapting periodontium afferent fibers were significantly larger than those of rapidly-adapting periodontium afferent fibers.     

The central projections of trigeminal primary afferent neurons in the cat as determined by the tranganglionic transport of horseradish peroxidase

The central projections of five peripheral branches of the trigeminal nerve were investigated by the method of transganglionic transport of horseradish peroxidase (HRP). In separate animals, the corneal, supraorbital, infraorbital, mental, or inferior alveolar branches were transected and soaked in concentrated solutions of HRP. Forty-eight to 72 hours after surgery, the brainstem, upper cervical spinal cord, and trigeminal ganglia were perfusion-fixed and processed according to the tetramethylbenzidine technique. The results show that trigeminal primary afferent neurons which innervate the cornea project mainly to the levels of caudal pars interpolaris and caudal pars caudalis. In contrast, trigeminal primary afferent neurons whose peripheral processes course through the supraorbital, infraorbital, or mental nerves project most heavily to the trigeminal main sensory nucleus, pars interpolaris, and the rostrocaudal middle three-fifths of pars caudalis. Trigeminal primary afferent neurons which give origin to the inferior alveolar nerve project heavily and in approximately equal numbers of all rostrocaudal levels of the trigeminal brainstem nuclear complex (TBNC). A small number of fibers from each of the latter four cell populations project directly to the contralateral C1-C2 dorsal horn. A small number of fibers from each cell population studied end in the reticular formation immediately adjacent to the spinal nucleus of V. It is concluded that the cornea and facial skin regions of the cat are represented nonuniformly along the rostrocaudal length of the TBNC.     

The central projections of tooth pulp afferent neurons in the rat as determined by the transganglionic transport of horseradish peroxidase

Transganglionic transport of horseradish peroxidase (HRP) or horseradish peroxidase-wheat germ agglutinin conjugate (HRP-WGA) was used to map in detail the central projections of trigeminal primary afferent neurons that innervate the dental pulp organ of the rat. In each of ten animals, 0.5-2.0 microliters of enzyme solution was injected into the pulp chamber of the first maxillary molar tooth. Postmortem examination of the decalcified teeth in all cases showed that the HRP/HRP-WGA remained confined to the pulp chamber and pulp roots, with no spread of enzyme into periapical tissues. HRP-labeled tooth pulp afferent fibers projected to all four rostrocaudal subdivisions of the ipsilateral trigeminal brainstem nuclear complex (TBNC) and to the upper cervical spinal cord. The labeled terminal fields formed a column that stretched relatively uninterrupted from just caudal to the rostromedial tip of the trigeminal principal sensory nucleus to at least the C2 segment of the spinal cord. The density of the afferent projection varied markedly from one rostrocaudal level of the TBNC to the next but was heaviest in an area encompassing the caudal one-half of the principal sensory nucleus and the rostral two-thirds of pars oralis. Fibers projected only lightly to pars caudalis, where they terminated preferentially in laminae I, IIa, and the junctional zone between laminae IV and V. HRP-labeled terminals in C1 and C2 were located almost exclusively in laminae I. In the dorsoventral axis, the terminal fields in the TBNC were located in a surprisingly dorsal part of the complex, well within what has been shown by others to be largely an area of termination for mandibular division fibers. Most fibers ended in medial parts of the TBNC, with the exception of two modestly labeled terminal fields located in the lateral aspects of rostral pars oralis and rostral pars caudalis. No labeled fibers terminated in the contralateral TBNC or contralateral cervical spinal cord.     

Identification and localization of the motor nuclei and sensory projections of the glossopharyngeal, vagus, and hypoglossal nerves of the cockatoo (Cacatua roseicapilla), Cacatuidae

Horseradish peroxidase (HRP) has been applied to the proximal severed ends of glossopharyngeal (N IX), vagus (NX), and hypoglossal (N XII) cockatoo in order to localize the motoneurons and sensory projections of these nerves which are involved in the control of the bird's feeding and phonatory behaviors. Application of HRP to N IX labeled four rhombencephalic nuclei: (1) a large-celled, retrofacial nucleus supplying M. geniohyoideus, the major tongue extensor; (2) a dorsal nucleus composed of medium-sized cells, projecting to most branches of N IX; (3) a ventrolateral nucleus supplying, amongst other structures, the floor of the pharynx and larynx; and (4) a ventral portion of the dorsal motor nucleus of the vagus. Neurons labeled by application of HRP to the cervical vagus comprise the classically defined dorsal motor nucleus and a ventrolateral medullary nucleus which is coextensive with that of the glossopharyngeus: together they probably constitute a nucleus ambiguus. Application of HRP to hypoglossal branches labeled a large nucleus intermedius (IM) and neurons ventral, ventrolateral, and caudal to it. The rostral third of IM supplies the lingual muscles, the caudal two-thirds the tracheosyringeal muscles. Many labeled neurons were found in the "jugular" ganglion following HRP treatment of each of the three nerves, especially N IX and N XII, which innervate the tongue. Central projections of these neurons are to nuclei of the descending trigeminus and to largely nonoverlapping portions of the principal trigeminal nucleus. It is hypothesized that these afferents provide sensory information necessary for the efficient processing and passage of food in the mouth.     

Expression of vanilloid receptor TRPV1 in the rat trigeminal sensory nuclei

Little is known about the central projection patterns of trigeminal afferent neurons expressing the vanilloid receptor TRPV1 and their coexpression of neuromodulatory peptides. To address these issues, we examined the distribution of TRPV1-positive neurons in the trigeminal ganglion (TG) and trigeminal sensory nuclei principalis (Vp), oralis (Vo), interpolaris (Vi), and caudalis (Vc) in the rat via light and electron microscopy. In addition, we studied the colocalization of TRPV1-positive neurons with substance P (SP) and calcitonin gene-related peptide (CGRP) via confocal microscopy. In TG, only small and medium-sized neurons were immunopositive for TRPV1. The staining for TRPV1 was found in axon collaterals in the dorsal parts of Vp, Vo, and Vi and in terminals and fibers throughout lamina I and the outer zone of lamina II (IIo) of Vc. With electron microscopy, TRPV1-positive fibers in the ascending and descending trigeminal tracts were found to be unmyelinated. Almost all TRPV1-positive terminals in Vc contained numerous large dense-core vesicles and formed synaptic contacts with single small dendrites. Multiple immunofluorescence revealed a high degree of colocalization of TRPV1 with SP and CGRP in TG neurons as well as in fibers and terminals confined to laminae I and IIo of Vc. These results suggest that the central projections of unmyelinated (C) afferents sensitive to noxious heat and capsaicin are organized differently between Vc and the rostral trigeminal nuclei and that Vc may play a role in the development of hyperalgesia.     

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

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)     

Somatosensory Trigeminal Projections to the Inferior Olive,Cerebellum and other Precerebellar Nuclei in Rabbits

We have analysed the pathways through which somatosensory information from the face reaches the inferior olive and the cerebellum in rabbits. We used wheatgerm agglutinin - horseradish peroxidase (WGA-HRP) to trace projections from all parts of the somatosensory trigeminal system to the olive, cerebellar cortex, the cerebellar deep nuclei and the pontine nuclei. Projections to the cerebellar cortex and inferior olive were verified using retrograde transport of WGA-HRP. Two regions of the inferior olive–the medial dorsal accessory olive and the ventral leaf of the principal olive–receive inputs from pars interpolaris (Vi) and rostral pars caudalis (Vc) of the spinal trigeminal nucleus and from the principal trigeminal nucleus (Vp). Another area in the caudal medial accessory olive receives inputs from rostral Vo (pars oralis of the spinal trigeminal nucleus), caudal Vi and Vc. There are trigemino-olivo-cortical inputs to lobule HVI via all these olivary areas and to the paramedian lobe via the principal olive only. Cerebellar cortex–lobules HVI, crus I and II, paramedian lobe and IX–receives direct mossy fibre inputs from Vp, Vo and rostral Vi. The pontine nuclei receive an input only from rostral Vi. We saw no trigeminal projections to other precerebellar nuclei or to the deep cerebellar nuclei. The concentration of face somatosensory cortical inputs, via several pathways, upon lobule HVI may underlie its important role in the regulation of learned and unlearned eyeblinks.     

Representation of upper and lower primary teeth in the trigeminal sensory nuclear complex in the young dog

Transganglionic transport of horseradish peroxidase-wheat germ agglutinin conjugate entrapped in polyacrylamide gel was used to study the patterns of termination of primary afferents that innervate the upper and lower primary tooth pulps within the trigeminal sensory nuclear complex of the young dog. The lower and upper primary tooth pulp afferents projected to the subnucleus dorsalis of the principal nucleus, the rostrodorsomedial part and subnucleus dorsomedialios (Vo.dm) of the parts oralis, the nucleus of the intermediate plexus (Vi.ip) of the pars interpolaris, and laminae I, II and V of the caudalis. The lower and upper primary teeth were topographically represented in the Vo.dm, rostrocaudal mid-levels of Vi.ip and in laminae I/V of the caudal levels of the pars caudalis, whereas an extensive overlapped projection was seen in other subdivisions.     

Somatotopic organization of tooth pulp primary afferent neurons in the cat

Transganglionic transport of horseradish peroxidase-wheat germ agglutinin conjugate (HRP-WGA) was used to study the somatotopic organization of pulpal afferent neurons innervating the different types of teeth in the trigeminal ganglion and trigeminal sensory nuclear complex (TSNC). In separate animals, the upper first 3 incisors (UI1-3), canine (UC), second premolar (UP2) and third premolar (UP3), and the lower first three incisors (LI1-3), canine (LC), first premolar (LP1), second premolar (LP2) and molar (LM) were traced in this experiment. Cell bodies innervating posterior teeth were found with greater frequency in dorsal maxillary ganglion regions, while somata supplying more anterior teeth were predominant ventrally. In contrast, cell bodies innervating the lower teeth were not arranged in a somatotopic fashion in the mandibular subdivision. Each pulpal afferent from lower and upper teeth projected to the subnucleus dorsalis (Vpd) of the pars principalis, the rostrodorsomedial (Vo.r) and dorsomedial parts (Vo.dm) of the pars oralis (Vo), the medial regions of the pars interpolaris (Vi), and laminae I, II, and V of the medullary dorsal horn, and terminal fields between the upper and lower teeth were separated in each subdivision. Pulpal projections from both the upper and lower teeth to each subdivision were organized in a somatotopic manner, while an extensive overlap in projections was noted between the adjoining teeth. In the Vpd, the upper and lower teeth were represented dorsoventrally, and projections from the anterior to posterior teeth in the upper jaw were arranged in both rostrocaudal and ventrodorsal sequences whereas those in the lower jaw were organized caudarostrally and lateromedially. In the Vo.r and Vo.dm, the upper and lower teeth were represented in a mediolateral sequence and projections from the anterior to posterior teeth were organized in a ventrolateral to dorsomedial sequence. In the Vi, pulpal projections were organized in a topographic fashion similar to that observed in the Vo.r and Vo.dm. In the medullary dorsal horn, the upper and lower teeth were represented in laminae I, II and V in a lateromedial sequence. Their projections to laminae I and V were topographically organized in a mediolateral and rostrocaudal sequence.(ABSTRACT TRUNCATED AT 400 WORDS)     

Afferent projections of the cervical vagus and nodose ganglion in the dog

The distribution within the brain stem of the afferent projections of the cervical vagus and the nodose ganglion was studied with horseradish peroxidase (HRP) and HRP-wheat germ agglutinin conjugate. Two to eight days after application of tracer into the cervical vagosympathetic trunk or the nodose ganglion the brain stems and ganglia were perfused and processed by the tetramethyl benzidine method. Vagal afferent fibers entered the lateral medulla as a distinct bundle spatially separate from the vagal efferent rootlets which were caudal and ventral to the afferents. Labeled axons in the solitary tract began to enter the nucleus tractus solitarii (nTS) 4.5 mm anterior to obex and were seen throughout the ipsilateral nTS as far as 3.5 mm caudal to obex. Label density varied within the nTS, with heaviest labeling in the dorsal and dorsolateral portions. Label was also seen in the ipsilateral area postrema (ap) and dorsal motor nucleus of the vagus. Labeled fibers crossed in the commissural portions of ap and nTS to enter the contralateral ap and nTS.     

Afferent connections of nervus facialis and nervus glossopharyngeus in the pigeon (Columba livia) and their role in feeding behavior

The afferent connections of the facial nerve and glossopharyngeal nerve in the pigeon have been studied with the Fink-Heimer I method after ganglion lesions. The nucleus ventrolateralis anterior of the solitary complex and an indistinct cell group S VII medial to the nucleus interpolaris of the descending trigeminal tract are the terminal fields for facial afferents. The n. ventrolateralis anterior also receives an important projection from the distal glossopharyngeal ganglion. Other projection areas of this ganglion are the n. presulcalis , n. centralis anterior, n. intermedius anterior and the parasolitary nucleus. Both ganglia have only ipsilateral projections. A lesion in the jugular ganglion complex causes degeneration throughout the ipsilateral solitary complex, in the contralateral n. commissuralis and n. centralis posterior and in the n. cuneatus externus. The lack of a substantial contribution to the trigeminal system is ascribed to the absence of mechanoreceptors in the tongue. The implications for the organization of neuronal pathways related to the feeding behavior are discussed.     

Afferent projections to the oral motor nuclei in the rat

Projections to the trigeminal, facial, ambiguus, and hypoglossal motor nuclei were determined by using horseradish peroxidase histochemistry. Most of the afferent projections to these motor nuclei were from the brainstem reticular formation, frequently in areas adjacent to other synergetic motor nuclei. The reticular formation lateral to the hypoglossal nucleus and reticular structures surrounding the trigeminal motor nucleus projected to each of these other brainstem motor nuclei involved in oral-facial function. Afferent projections to these motor nuclei also were organized along the rostrocaudal axis. Within the reticular formation most of the afferent projections to the trigeminal motor nucleus originated rostral to the majority of neurons projecting to the hypoglossal and ambiguus nuclei, which in turn were rostral to the primary source of reticular afferents to the facial nucleus. In comparison, projections from the sensory trigeminal nuclei and nucleus of the solitary tract were sparse. The interneuron pools that project to the orofacial motoneurons provide one further link in understanding the brainstem substrates for integrating oral and ingestive behaviors.     

The central projections of the trigeminal,facial and anterior lateral line nerves in the carp (Cyprinus carpio L.)

The central projections of the trigeminal, facial and anterior lateral line nerves were studied in the carp (Cyprinus carpio) by the Nauta and Fink-Heimer silver techniques following rhizotomy. Degenerating trigeminal fibers were found projecting on the nucleus of the descending trigeminal root and on the medial funicular nucleus. The former can be subdivided in five portions lying dorsal to the various cranial motor nuclei. The afferent facial fibers could be traced into the facial, glossopharyngeal and vagal lobes, while the anterior lateral line nerve projects on rostral, medial and caudal parts of the medial nucleus and on the eminetia granularis. The anterior lateral line nerve can be divided into a dorsal and a ventral root, each following the same course. The role trigeminal and facial nerves play in proprioception of respiratory muscles is discussed.