Thalamocortical projections to layer I of the primary auditory cortex in the cat: a horseradish peroxidase study

HRP injected into layer I of the primary auditory cortex (AI) in the cat labeled neuronal cell bodies ipsilaterally in the medial, dorsal and ventrolateral divisions of the medial geniculate nucleus (MGN), suprageniculate nucleus, and nucleus of the brachium of the inferior colliculus. MGN neurons labeled after HRP injected into layer I were statistically smaller than those labeled after HRP injected into layer IV.     

Central projections of the normal and ‘regenerate’ infraorbital nerve in adult rats subjected to neonatal unilateral infraorbital lesions: a transganglionic horseradish peroxidase study

The visuotopic organization of the primary visual cortex (area 17) and the extrastriate visual regions surrounding it (areas 18a and 18) has been studied in gray rats using standard microelectrode mapping techniques. The results confirm and extend previous observations in the rat. Apart from the representation of the contralateral visual field (VF) in area 17, in which the upper VF is represented caudally and the nasal VF laterally, there are additional representations of the VF in the extrastriate cortex. In lateral extrastriate cortex (area 18a) there are at least 4 such representations, namely lateromedial (LM), anterolateral (AL), laterointermediate (LI) and laterolateral (LL). In LM (second visual area) the upper VF is represented caudally and the nasal VF medially, being thus a mirror image of V1. In AL (third visual area) the upper VF is represented rostrally and the nasal VF, medially, being thus a mirror image of LM. In LI, the upper VF is medial and the nasal VF, lateral, being thus a mirror image of LM, or a reduced copy of V1. In medial extrastriate cortex (area 18) there are two representations of the temporal VF, labeled anteromedial (AM) and posteromedial (PM). In AM, the upper temporal VF is medial and the lower temporal VF, lateral, the extreme temporal field being rostral. The 30 degrees azimuth provides the boundary between AM and PM. Thus, AM is organized as a counter-clockwise rotation by 90 degrees of the V1 representation. In PM, the upper lower VF topography is like in AM, but the extreme temporal VF is caudal, being thus a mirror image of AM.     

Differential distribution of cell bodies and central axons of mesencephalic trigeminal nucleus neurons supplying the jaw-closing muscles and periodontal tissue: A transganglionic tracer study in the cat

Distribution of cell bodies and central axons of mesencephalic trigeminal nucleus (MTN) neurons were examined in the cat by the method of transganglionic transport of horseradish peroxidase (HRP). Jaw-closing muscle afferent MTN neurons were distributed throughout the whole rostrocaudal extent of the MTN, and sent their axons ipsilaterally to the supratrigeminal and intertrigeminal regions, dorsolateral division of the motor trigeminal nucleus, lateral part of the medullary reticular formation, lamina VI of C1-C3 cord segments, and cerebellum. On the other hand, periodontal receptor afferent MTN neurons were located mainly in the caudal part of the MTN, and sent their axons ipsilaterally to the supratrigeminal region and cerebellum. The existence of multipolar MTN neurons with 1-9 smooth dendrites was also confirmed; most of them were jaw-closing muscle afferent neurons.     

Projections from C2 and C3 nerves supplying muscles and skin of the cat neck: a study using transganglionic transport of horseradish peroxidase

Transganglionic transport of HRP has been used to trace the pathways and termination sites of cutaneous and muscle afferent axons entering from the C2 and C3 dorsal rami. The muscle afferent projection in the spinal cord is restricted and (apart from the ventral horn) largely confined to the intermediate gray matter. There is a muscle afferent projection to the ventrolateral main cuneate nucleus and a complex pattern of projection through the extent of the external cuneate nucleus. In contrast, the cutaneous spinal projection is abundant with extensive filling of axons in the tract of Lissauer and many termination sites in the lateral substantia gelatinosa. Axons enter the lateral gray matter of the cervical spinal cord from the dorsal columns and the dorsolateral funiculus and terminate in the lateral one-third of the dorsal horn as far rostral as the spinomedullary junction. Axons of the tract of Lissauer form a complex web around the dorsal horn and many penetrate rostrally to the region of the spinomedullary junction, where they terminate among clusters of interstitial cells on and close to the dorsal medullary surface. Cutaneous afferent axons from the dorsal columns turn into the main cuneate nucleus and enter a dense mass of HRP-reaction product which occupies the most ventrolateral part of the nucleus for its entire length.     

The afferent projections to the centrum medianum of the cat as demonstrated by retrograde transport of horseradish peroxidase

The afferent projections of nucleus centrum medianum (CM) of the thalamus were studied, in the cat, by means of retrograde transport of electrophoretically ejected horseradish peroxidase. Several variations of method — survival time, fixatives, substrates, etc. — were tried to improve the amount of visible reaction product.Labeled neurons were localized primarily in two categories of nuclei in the brain. The first consisted of structures making up or closely related to the basal ganglia: the entopeduncular nucleus, the pars reticulata of the substantia nigra, and motor cortex. The second category was made up of nuclei closely related to postural and orienting functions: the deep layers of the superior colliculus ipsilaterally, and the medial and lateral vestibular nuclei bilaterally. Other nuclei containing retrogradely labeled neurons were the periaqueductal gray and locus coeruleus. Brain stem reticular projections were sparse and widely scattered. These results identify CM as an important element in the loop system linking medial thalamus and neostriatum; the probable attention and orientation related functions of this system are discussed.     

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.     

Thalamic projections of nucleus reticularis thalami of cat: a study using retrograde transport of horseradish peroxidase and fluorescent tracers

The retrograde transport of horseradish peroxidase (HRP) and fluorescent tracers after injections in various thalamic nuclei was used to investigate the relative density of retrogradely labeled cells in different districts of reticularis thalami (RE) nuclear complex of cat. The RE nucleus was left virtually free of labeling only after injections localized into the anterior nuclear group; in those experiments, heavy retrograde labeling was obtained in mammillary nuclei. The major targets of RE cells proved to be centralis lateralis-paracentralis (CL-PC) and centrum medianum-parafascicularis (CM-PF) intralaminar nuclei. The projections to various intralaminar nuclei mainly arise in the rostral pole and rostrolateral part of RE nucleus and are reciprocal to intralaminar-RE pathways disclosed by Jones ('75). The RE territories labeled following injections in relay and associational nuclei are more restricted and are located contiguously and slightly anteriorly to a given nucleus. There was a very small proportion of doubly labeled RE cells after injections with fluorescent tracers in different nuclei. This was not due to a technical failure since many double-labeled neurons were found in the same material in medial globus pallidum after thalamic and midbrain injections (see companion paper by Parent and Steriade, '84). We conclude that most individual RE axons arborize in only one thalamic nucleus or nuclear group. An additional finding was the existence of intralaminar-to-relay (CL-PC to VA-VL) projections.     

Central distribution of primary afferent fibers in the Arnold's nerve (the auricular branch of the vagus nerve): A transganglionic HRP study in the cat

Central projections of the Arnold's nerve (the auricular branch of the vagus nerve; ABV) of the cat were examined by the transganglionic HRP method. After applying HRP to the central cut end of the ABV, HRP-labeled neuronal somata were seen in the superior ganglion of the vagus nerve. Main terminal labeling was seen ipsilaterally in the solitary nucleus, in the lateral portions of the ventral division of the principal sensory trigeminal nucleus, in the marginal regions of the interpolar subnucleus of the spinal trigeminal nucleus, in the marginal and magnocellular zones of the caudal subnucleus of the spinal trigeminal nucleus, in the ventrolateral portions of the cuneate nucleus, and in the dorsal horn of the C1–C3 cord segments. In the solitary nucleus, labeled terminals were seen in the interstitial, dorsal, dorsolateral and commissural subnuclei; some of these terminals may be connected monosynaptically with solitary nucleus neurons which send their axons to the somatomotor and/or visceromotor centers in the brainstem and spinal cord.     

Ultrastructure of transganglionic HRP transport in cat trigeminal system

The ultrastructure of transganglionic transport of horseradish peroxidase (HRP) from the inferior alveolar (IA) nerve to the brainstem is being studied in the cat. The IA nerve was soaked in an HRP solution and following a two-day survival the animal was perfused transcardially with a paraformaldehyde-glutaraldehyde solution. The tissue was immediately dissected and postfixed for 1-3 h in perfusate. Sections of 75 micron thickness were cut with a Vibratome and reacted utilizing tetramethyl benzidine (TMB) as the chromagen. Optimum results for electron microscopy were obtained by osmication in a pH 6.0, 1% osmium tetroxide solution for 45 min at 45 degrees C, followed by rapid dehydration and embedment in Epon. The resulting HRP-TMB reaction product was characterized and identified ultrastructurally in ganglion cells, peripheral and central axons and in brainstem terminals. The HRP-TMB reaction product varied in density but had consistent crystalline-like laminations of a repeating unit and characterized by a membrane 4-5 nm in diameter. Some of the HRP-TMB reaction product found in terminals and axons was below the limit of resolution of the light microscope.     

Laminar-related projection of primary trigeminal fibers in the caudal medulla demonstrated by transganglionic transport of horseradish peroxidase

The mode of termination of primary afferent fibers within the cat trigeminal nucleus caudalis was investigated by means of the transganglionic transport of horseradish peroxidase (HRP). Several types of laminar-related labeling were observed, depending upon the survival time after HRP application. At the earliest survival time (28–34 h) the highest density of labeling was found in laminae I and II. At 2 and 3 days survival laminae III and IV were heavily labeled, in addition to laminae I and II where the amount of labeling was greatly increased in lamina I, but not in lamina II. At 5 days survival time an abrupt drop of labeling occurred in laminae I and II, while this pattern was not predominant in laminae III and IV. In lamina V the pattern of labeling was less intense and not changeable through all survival times observed. These findings indicating a differentiation of the primary afferent terminals have good correspondence with a functional specialization of neuronal locations since the functional properties of neurons vary according to their locations.     

Central projections of the rat radial nerve investigated with transganglionic degeneration and transganglionic transport of horseradish peroxidase

Transganglionic degeneration and transganglionic transport of HRP were used for investigation of the spinal cord and brainstem projections from the superficial, cutaneous (SR) and deep, muscular (DR) branches of the radial nerve. The HRP study included a numerical and size analysis of labelled dorsal root ganglion (DRG) cells. In degeneration experiments the SR nerve was found to project somatotopically to laminae III-IV, but degeneration was also found in lamina I and inconsistently in lamina II. Transection of the DR nerve was found to give rise to a small amount of degeneration, which in "sham" operations was established to result from the skin injury during dissection of the DR nerve. With the HRP method, the SR nerve was found to project somatotopically to laminae I-IV, whereas the DR nerve projected more diffusely to the medial part of laminae V-VII. HRP application to the SR and DR nerves resulted in labelling of a mean of 1,024 and 310 DRG cells, respectively. These labelled neurons had a median cell area of 381 and 562 micron 2 for the SR and DR nerves, respectively, and both small and large cells were labelled in both types of experiments. In the lower brainstem, projections from the SR nerve were found only in the ipsilateral dorsal part of the main cuneate nucleus (MCN) with both methods. Brainstem projections from the DR nerve that were found only with the HRP method were found in the ipsilateral ventral part of the MCN together with a projection to the ipsilateral external cuneate nucleus. No projections were found to the central cervical nucleus. The present results indicate that cutaneous compared to muscular primary sensory neurons are much more prone to react with transganglionic degeneration after peripheral nerve transection. Furthermore, in the rat the SR nerve projects somatotopically, whereas the DR nerve does not. Both nerve branches are connected to small and large spinal ganglion cells, although the median cell area is larger in muscular neurons.     

Segmental distribution and central projectionsof renal afferent fibers in the cat studied by transganglionic transport of horseradish peroxidase

The segmental and central distributions of renal nerve afferents in adult cats and kittens were studied by using retrograde and transganglionic transport of horseradish peroxidase (HRP). Transport of HRP from the central cut ends of the left renal nerves labeled afferent axons in the ipsilateral minor splanchnic nerves and sensory perikarya in the dorsal root ganglia from T12 to L4. The majority of labeled cells (85%) were located between L1 and L3. A few neurons in the contralateral dorsal root ganglia were also labeled. Labeled cells were not confined to any particular region within a dorsal root ganglion. Some examples of bifurcation of the peripheral and central processes within the ganglion were noted. A small number of preganglionic neurons, concentrated in the intermediolateral nucleus, were also identified in some experiments. In addition, many sympathetic postganglionic neurons were labeled in the renal nerve ganglia, the superior mesenteric ganglion, and the ipsilateral paravertebral ganglia from T12 to L3 Transganglionic transport of HRP labeled renal afferent projections to the spinal cord of kittens from T1 1 to L6, with the greatest concentrations between Ll and L3. These afferents extended rostrocaudally in Lissauer's tract and sent collaterals into lamina I. In the transverse plane, a major lateral projection and a minor medial projection were observed along the outer and inner margins of the dorsal horn, respectively. From the lateral projection many fibers extended medially in laminae V and VI forming dorsal and ventral bundles around Clarke's nucleus. The dorsal bundle was joined by collaterals from the medial afferent projection and crossed to the contralateral side. The ventral bundle extended into lamina VII along the lateroventral border of Clarke's nucleus. Some afferents in the lateral projection could be followed ventrally into the dorsolateral portion of lamina VII in the vicinity of the intermediolateral nucleus. In the contralateral spinal cord, labeled afferent fibers were mainly seen in laminae V and VI These results provide the first anatomical evidence for sites of central termination of renal afferent axons. Renal inputs to regions (laminae I, V, and VI) containing spinoreticular and spinothajamic tract neurons may be important in the mediation of supraspinal cardiovascular reflexes as well as in the transmission of activity from nociceptors in the kidney. In addition, the identification of a bilateral renal afferent projection in close proximity to the thoracolumbar autonomic nuclei is consistent with the demonstration in physiological experiments of a spinal pathway for the renorenal sympathetic reflexes.     

Primary neurons maintain their central axonal arbors in the spinal dorsal horn following peripheral nerve injury: an anatomical analysis using transganglionic transport of horseradish peroxidase

This study in adult cats demonstrates that primary neurons of all sizes survive following the transection and capping with a polyethylene tube of their peripheral processes in the superficial radial nerve. The central axonal arbors of these injured primary neurons remain intact and maintain their normal topographic position across laminae I–VI of the cervical (C6–C8) dorsal horn. In addition, they maintain their synaptic vesicles, some of their synaptic connections and their ability to transport horseradish peroxidase transganglionically.     

Restlessness in suboccipital muscles as a manifestation of akathisia

Antipsychotic-induced akathisia is primarily manifested as restlessness, particularly expressed in the legs. Consequently, rating scales and the research criteria of DSM-IV regard restlessness in the legs as the major sign of akathisia, although it has been suggested that such restlessness may occur in other areas of the body. A case of antipsychotic-induced akathisia is reported where the region of inner restlessness (the subjective component) was identified in posterior cervical muscles. The patient was initially suspected to be experiencing somatic delusions and the dose of antipsychotic medication was increased. This did not improve the symptoms, and upon careful questioning about his head discomfort, the patient acknowledged that he felt an inner restlessness in the suboccipital muscles. The restlessness ceased with intramuscular biperiden and subsequent discontinuation of antipsychotic medication. This case suggests that subjective restlessness may occur in muscle groups that are not usually associated with akathisia. Thus, this report may assist clinicians in the diagnosis of akathisia that could be overlooked or misdiagnosed as somatic delusions or the worsening of the patient's psychosis.     

Central distribution of trigeminal and upper cervical primary afferents in the rat studied by anterograde transport of horseradish peroxidase conjugated to wheat germ agglutinin

Injections of WGA-HRP were made in the rat trigeminal ganglion and C1-3 dorsal root ganglia (DRGs) to study the central projection patterns and their relations to each other. Trigeminal ganglion injections resulted in heavy terminal labeling in all trigeminal sensory nuclei. Prominent labeling was also observed in the solitary tract nucleus and in the medial parts of the dorsal horn at C1-3 levels, but labeling could be followed caudally to the C7 segment. Contralateral trigeminal projections were found in the nucleus caudalis and in the dorsal horn at C1-3 levels. The C1 DRG was found to be inconstant in the rat. When it was present, small amounts of terminal labeling were found in the external cuneate nucleus (ECN) and the central cervical nucleus (CCN). No dorsal horn projections were seen from the C1 DRG. Injections in the C2 DRG resulted in heavy labeling in the ECN, nucleus X, CCN, and dorsal horn, where it was mainly located in lateral areas. Labeling could be followed caudally to the Th 7 segment. C2 DRG projections also appeared in the cuneate nucleus (Cun), in all the trigeminal sensory nuclei, and in the spinal, medial, and lateral vestibular nuclei. A small C2 DRG projection was observed in the ventral cochlear nucleus. C3 DRG injections resulted in heavy labeling in both medial middle and lateral parts of the dorsal horn, in the ECN, and in nucleus X, whereas the labeling in the CCN was somewhat weaker. Smaller projections were seen to trigeminal nuclei, Cun, and the column of Clarke. Comparisons of the central projection fields of trigeminal and upper cervical primary afferents indicated a somatotopic organization but with a certain degree of overlap.     

An HRP study of the central course of sensory intermediate and vagal fibers in peripheral facial nerve branches in the cat

Previous studies have shown that sensory fibers of intermediate and vagal nerve origin are present in facial nerve branches to the mimetic muscles in the cat. In the present study the central course of these fibers has been examined by transganglionic transport of horseradish peroxidase (HRP). In some of these experiments the facial nerve proper was transected central to the site of HRP application. In this way, the central course of the vagal fibers could be studied separately. For comparison HRP-conjugated wheat germ agglutinin was injected into the geniculate ganglion, revealing the central course of the entire afferent component of the intermediate nerve. The results show that labeled sensory intermediate nerve fibers, at their level of entrance in the brainstem, form a tract at the dorsal margin of the spinal trigeminal tract (5T). While some fibers ascend from this level to terminate in the main sensory trigeminal nucleus, and a few fibers terminate in the rostral part of the solitary tract nucleus, the majority take a descending course. The main site of termination for these descending fibers is in the medial part of the C2 dorsal horn. Terminal labeling is also seen in the ventrolateral part of the cuneate nucleus (CUN) and in a small area of gray substance between CUN and trigeminal nucleus caudalis. After entering the brainstem some sensory vagal fibers project to the trigeminal nucleus interpolaris and to an interstitial nucleus within the 5T, but the larger part joins the descending tract of intermediate nerve fibers. These descending vagal fibers have a terminal distribution pattern similar to the intermediate nerve fibers.     

Tracing of afferent and efferent pathways in the left inferior cardiac nerve of the cat using retrograde and transganglionic transport of horseradish peroxidase

Retrograde and transganglionic transport of horseradish peroxidase (HRP) was used to trace afferent and efferent pathways in the left inferior cardiac nerve of the cat. Cardiac efferent and afferent neurons were located, respectively, in the stellate ganglion (average cell count per experiment: 2679) and in the ipsilateral dorsal root ganglia (DRG) from C8 to T9 (average cell count per experiment: 213). Labeled cardiac afferent projections to the spinal cord were most dense in segments T2–T6 where they were located in Lissauer's tract and in lamina 1 on the lateral border of the dorsal horn. Labeled affrent axons extended ventrally through lamina 1 into lamina 5 and the dorsolateral region of lamina 7 in proximity to the intermediolateral nucleus. A weak projection was noted on the medial side of the dorsal horn. These sites of termination are similar to projections by other sympathetic afferent pathways (i.e. renal, hypogastric and splanchnic nerves) to the lower thoracic and lumbar spinal cord, indicating that visceral afferents may have a uniform pattern of termination at various segmental levels. This pattern of termination in regions of the gray matter containing spinothalamic tract neurons and neurons involved in autonomic mechanisms is consistent with the known functions of sympathetic afferent pathways in nociception and in the initiation of autonomic reflexes.     

Efferent projections of the interpeduncular complex in the rat, with special reference to its subnuclei: a retrograde horseradish peroxidase study

Projections of the subnuclei of the interpeduncular complex were studied by the retrograde horseradish peroxidase technique in the rat. The pars caudalis and pars dorsalis magnocellularis project to the septum, hippocampus and entorhinal cortex; a part of the pars medialis and the pars paramediana, to the dorsal thalamus; all subnuclei, to the midbrain raphe; and the pars lateralis, to the dorsal tegmental nucleus.     

Morphological identification of brain stem neurones associated with predatory behaviour elicited by lateral hypothalamic electrical stimulation in the cat: a retrograde transport study using horseradish peroxidase subsequent to an electrolytic lesion

The combination of electrical stimulation of the lateral hypothalamus to elicit predatory behaviour, an electrolytic lesion and a subsequent HRP injection was used to identify brain stem neurones whose axons were affected by such hypothalamic stimulation. In contrast, the injection of HRP into such hypothalamic sites, without a prior lesion, resulted in a significant reduction in the number of labelled neurones. This suggests that an important contribution, namely those neurones which give rise to fibres which pass through the stimulated region, is underestimated by the later procedure.     

Infrared sensory neurons in the trigeminal ganglia of crotaline snakes: transganglionic HRP transport

Trigeminal neurons were labeled by inserting HRP into holes cut in the pit receptor membranes of a crotaline snake, Agkistrodon blomhoffi brevicaudus. Neurons were labeled in the ophthalmic ganglion and the maxillary division of the maxillo-mandibular ganglion, and the HRP was further transported across the ganglia and through the lateral descending trigeminal tract (dlv) to label axon terminals exclusively in the dlv nucleus (DLV). In 6 successful preparations, 7.1-19.3% of totals of 5568-5986 cells in the maxillary division of the ganglion were labeled, but none at all were labeled in the mandibular division. Only a few or none at all were labeled in the ophthalmic ganglion. Cells in the two ganglia ranged in size from 10 to 55 micrometers, but large cells (greater than or equal to 40 micrometers) were scarce (4.9% of the total population). All HRP-labeled neurons fell in the median range of 20-39 micrometers. We concluded that these ganglion cells were infrared neurons, and were therefore the origin of the A delta fibers in the pit membrane. There were no HRP-labeled neurons above or below this range, in spite of the fact that smaller cells (less than or equal to 19 micrometers) made up 35.8% of the total population. In normal Nissl preparations we found both light- and dark-staining cells, but the size range of neither corresponded to the size range of infrared neurons.