Transport Of Wheat Germ Agglutinin Research Articles

Transneuronal Transport of Wheatgerm Agglutinin Conjugated with Horseradish Peroxidase in the Somatosensory System of the Rat: A Light- and Electron-Microscopic Study

Experiments were performed in order to investigate, at the light- and electron-microscopic levels, the transneuronal transport of wheatgerm agglutinin conjugated with horseradish peroxidase (WGA:HRP) in the somatosensory system of rats. In five adult albino rats, various amounts of WGA:HRP at different concentrations were bilaterally injected in the dorsal column nuclei (DCN). In one additional animal, WGA:HRP was injected in one side, whereas free HRP was injected in the contralateral DCN. In another five rats, WGA:HRP was injected in the first somatosensory cortex (SI). The postinjection survival time of the animals ranged from 30 to 48 hr. The histochemical visualization of the enzyme was performed using either paraphenylenediamine-pyrocatechol (PPD-PC) or tetraethylbenzidine (TMB) as chromogens on adjacent horizontal serial sections. All the reacted samples were studied at the light-microscopic level, and sections from four animals were processed for the ultrastructural investigation. After DCN injections, a massive anterograde labeling was always observed in nucleus ventralis posterolateralis (VPL) of the thalamus, where also labeled neurons and glial cells were detected at both the light- and the electron-microscopic levels. Labeled neurons and terminals in the lateral border of nucleus reticularis (Re) of the thalamus were also observed after either DCN or SI injection of WGA:HRP. Our results show that WGA:HRP is effectively transported not only anterogradely and retrogradely through the somatosensory system of the rat, but also transneuronally. The transneuronal transfer of the tracer seems to be mainly related to the postlabeling survival time of the animal, and it does not occur when free HRP is injected. In controlled experimental conditions, WGA:HRP can therefore be useful for tracing secondary projections. Moreover, in the present report, the existence of a mediolateral arrangement of the projections of the somatosensory-related area of Re toward VPL is directly demonstrated. As for the histochemical procedure employed, differences in sensitivity are shown between PPD-PC and TMB, although the same general pattern of labeling is present with both chromogens.

The connections of the mouse olfactory bulb: A study using orthograde and retrograde transport of wheat germ agglutinin conjugated to horseradish peroxidase

The efferent and centrifugal afferent connections of the main olfactory bulb (MOB) of the mouse were studied by orthograde and retrograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). MOB projects ipsilaterally to the anterior olfactory nucleus, taenia tecta, anterior hippocampal continuation, indusium grisium, olfactory tubercle, and the lateral and medial divisions of the entorhinal area. In the region of the anterior one-half to two-thirds of the posterior division of the insular cortex the projection from MOB extends into the insular cortex. The only efferent projection of MOB to the contralateral half of the brain was to the anterior olfactory nucleus. All efferent projections of MOB, thus, are to telencephalic structures. By contrast the centrifugal afferents to MOB originate from every major division of the neuraxis. Neurons projecting to the bulb were found ipsilaterally in all divisions of the anterior olfactory nucleus (AON). In some cases, labeling in the external division of AON was weak or absent. In the contralateral AON, pars externa was the most intensively labeled sub-division. Retrogradely labeled neurons were also present in all other subdivisions of the contralateral AON but were fewer in number and less heavily labeled than in the ipsilateral AON. Ipsilaterally, positive neurons were also present in taenia tecta, and the anterior hippocampal continuation. There was profuse retrograde labeling of neurons in the entire extent of the ipsilateral piriform cortex (PC). There was a rostral to caudal gradient of labeling in PC with more positive neurons in rostral than caudal parts. Labeled neurons were present in the lateral entorhinal cortex LEC and in the transitional cortex between LEC and PC. Very heavy retrograde labeling was present in the nuclei of the horizontal and vertical limbs of the diagonal band (HDB and VDB). More cells were labeled in HDB than in VDB. Neurons were labeled in the ipsilateral nucleus of the lateral olfactory tract (NLOT) and, when the injection spread into the accessory olfactory bulb, labeled neurons were present ventral to NLOT in accessory NLOT. A few lightly labeled neurons were always present in the posterolateral and medial cortical amygdaloid areas. Neurons were labeled in the zona inserta and scattered throughout several hypothalamic nuclei. There was massive retrograde labeling of neurons in the locus coeruleus and neurons were abundantly labeled in the dorsal and medial raphe nuclei and nucleus raphe pontis. In general, the labeling of MOB connections was more extensive than that which has been reported in closely related species.(ABSTRACT TRUNCATED AT 400 WORDS)

Cortical projections of the nucleus of the diagonal band of broca and of the substantia innominata in the rat: An anatomical study using the anterograde transport of a conjugate of wheat germ agglutinin and horseradish peroxidase

The projections of the nucleus of the diagonal band of Broca and of the substantia innominata to the cerebral cortex were studied in the rat, using the anterograde transport of wheat germ agglutinin conjugated with horseradish peroxidase. Following diagonal band injections, fibers were observed ascending in the septum and reaching the cingulate cortex. They had a rostrocaudal, horizontal direction, mostly in layer VI and could be followed over long distances on sagittal sections. The fibers gave off collaterals which were seen ascending in the cerebral cortex and reaching more superficial layers. Following substantia innominata injections, fibers were observed to take two routes: the first one identical to the one described above and a second through the caudate-putamen reaching the temporo-insular cortex. Terminal fields had a more diffuse distribution following substantia innominata than following diagonal band injections. No clear laminar pattern of termination was observed. However the density of terminals was higher in layers IV, V and VI than in layers I, II and III. Since the conjugate used is not taken up by fibers of passage, this pattern of connection is believed to reflect the organization of the projection of the nucleus of the diagonal band and of the substantia innominata to the cerebral cortex.

The organization of projections from the cortex, amygdala, and hypothalamus to the nucleus of the solitary tract in rat.

Direct projections from the forebrain to the nucleus of the solitary tract (NTS) and dorsal motor nucleus of the vagus in the rat medulla were mapped in detail using both retrograde axonal transport of the fluorescent tracer True Blue and anterograde axonal transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). In the retrograde tracing studies, cell groups in the medial prefrontal cortex, lateral prefrontal cortex (primarily ventral and posterior agranular insular cortex), bed nucleus of the stria terminalis, central nucleus of the amygdala, paraventricular, arcuate, and posterolateral areas of the hypothalamus were shown to project to the NTS and in some cases also to the dorsal motor nucleus of the vagus. The prefrontal cortical areas projecting to the NTS apparently overlap to a large degree with those cortical areas receiving mediodorsal thalamic and dopaminergic input. The retrogradely labeled cortical cells were situated in deep layers of the rat prefrontal cortex. The anterograde tracing studies revealed a prominent topography in the mediolateral termination pattern of forebrain projections to the rostral part of the NTS and to the dorsal pons. The projections to the NTS were generally bilateral, except for projections from the central nucleus of the amygdala and bed nucleus of the stria terminalis which were predominantly ipsilateral. The prefrontal cortical projections to the NTS travel through the cerebral peduncle and pyramidal tract and terminate throughout the rostrocaudal extent of the NTS. Specifically, the prefrontal cortex innervates dorsal portions of the NTS (lateral part of the dorsal division of the medial solitary nucleus, dorsal part of the lateral solitary nucleus and the caudal midline region of the commissural nucleus), areas which receive relatively sparse subcortical projections. These dorsal portions of the NTS receive major primary afferent projections from the vagal and glossopharyngeal nerves. In contrast, the subcortical projections, which travel through the midbrain and pontine tegmentum, terminate most heavily in the ventral portions of the NTS, i.e., the area immediately dorsal and lateral to the dorsal motor nucleus of the vagus. Only the paraventricular hypothalamic nucleus has substantial terminals throughout the dorsal motor nucleus of the vagus. Hypothalamic cell groups innervate the area postrema and, along with the prefrontal cortex, innervate the zone subjacent to the area postrema.(ABSTRACT TRUNCATED AT 400 WORDS)

Anatomical evidence for convergence of olfactory, gustatory, and visceral afferent pathways in mouse cerebral cortex

Flavor perception requires the neural integration of olfactory, gustatory and, possibly, visceral afferent information. Presently, it is not known where, or how this integration takes place in the brain. Neuroanatomical data presented here suggest that pathways subserving these sensory modalities converge in mouse insular cortex after surprisingly few synaptic relays. Orthograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) was used to label main olfactory bulb (MOB) efferents. A projection into layer I of insular cortex was present in every case. Bulb transections were made to provoke anterograde degeneration and EM analysis confirmed that the olfactory projection to insular cortex was a terminal pathway. WGA-HRP injections in the MOB-recipient zone of insular cortex resulted in ortho and retrograde labeling of ascending and descending gustatory-visceral afferent pathways. It is concluded that in the mouse, there is a remarkably direct convergence of olfactory and gustatory-visceral sensory pathways in insular cortex. Together with the descending connections from insular cortex to the amygdala and to brainstem autonomic structures, it is possible that the cortical integration of olfactory and gustatory-visceral information could modulate mechanisms involved in food selection and autonomic reactions relating to the chemical senses. Basic mechanisms subserving flavor perception might be usefully modelled in mouse insular cortex.

Cerebellar Autonomic Function: Direct Hypothalamocerebellar Pathway

A direct hypothalamocerebellar projection in the cat was revealed by means of retrograde transport of wheat germ agglutinin--horseradish peroxidase complex. This appears to be the first demonstration of a significant autonomic input to the cerebellum. The projection has a widespread origin and is bilateral with an ipsilateral preponderance.

The origin of thalamic inputs to the arcuate premotor and supplementary motor areas

We have used retrograde transport of wheat germ agglutinin conjugated to horseradish peroxidase to examine the origin of thalamic input to the two premotor areas with the densest projections to the motor cortex: the arcuate premotor area (APA) and the supplementary motor area (SMA). Retrograde transport demonstrated that the two premotor areas and the motor cortex each receive thalamic input from separate, cytoarchitectonically well defined subdivisions of the ventrolateral thalamus. According to the nomenclature of Olszewski (Olszewski, J. (1952) The Thalamus of the Macaca mulatta. An Atlas for Use with the Stereotaxic Instrument, S. Karger, AG, Basel), input to the APA originates largely from area X, input to the SMA originates largely from the pars oralis subdivision of nucleus ventralis lateralis (VLo), and that to the motor cortex originates largely from the pars oralis subdivision of nucleus ventralis posterior lateralis (VPLo). These observations, when combined with prior studies on the termination of various subcortical efferents in the thalamus, lead to the following scheme of connections: (1) rostral portions of the deep cerebellar nuclei project to the motor cortex via VPLo; (2) caudal portions of the deep cerebellar nuclei project to the APA via area X; and (3) the globus pallidus projects to the SMA via VLo. Thus, each thalamocortical pathway is associated with a distinct subcortical input.

Laminar origin of the tecto-thalamic projections in the albino rat

Cells of origin of the tecto-LP (lateroposterior nucleus of the thalamus) projection and the tecto-LGNd (dorsal nucleus of the lateral geniculate body) projection were studied in the albino rat by means of retrograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). Tecto-LGNd neurons with small spindle form were located in the stratum griseum superficiale of the superior colliculus (SC), whereas tecto-LP neurons with polygonal shape were found in the stratum opticum of the SC.

The terminations of the spinothalamic tract in the cat

The termination sites of the spinothalamic tract (STT) in the cat have been examined using the anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). Cats which received an injection of WGA-HRP at the spinal cervical level (C7–C8) displayed anterograde labelling in the ventral posterior lateral (VPL), ventrolateral, lateral posterior, limitans, suprageniculate, medial geniculate pars magnocellularis, central lateral, paracentral, centrum medianum, submedius, central medial, reuniens, rhomboid and periventricular thalamic nuclei. Lumbar injection (L2–L3) produced a similar although less intense pattern of labelling, with only the VPL displaying an obvious topological organization. Although the STT terminations in the cat appear to be less dense than those observed in the rat or monkey the present results demonstrate that in the cat a widely variety of thalamic nuclei receive a direct STT projection and that the cat VPL, like rat, monkey and man receives a direct STT input.

Efferent connections of the subfascicular area of the mesodiencephalic junction and its possible involvement in stimulation-produced analgesia

Stimulation-produced analgesia (SPA) can be induced in animals and humans from an ill-defined area of the mesodiencephalic junction lying beneath the parafascicular complex of the medial thalamus. Neurons projecting to the spinal cord, the subnucleus caudalis of the trigeminal complex, the nuclei raphe´magnus and dorsalis, the imferior olivary complex and the amygdala could be observed in this area, using the retrograde transport of wheat germ agglutinin conjugated to horseradish peroxidase. On the basis of the locations of the neurons projecting to these different areas, 3 subnuclei were delineated: the rostral interstitial nucleus of the MLF lying laterally along the medial tip of the medial lemniscus, containing a few neurons projecting to the raphe´nuclei and the inferior olivary complex; the subparafascicular nucleus (spf) lying medially in the rostralmost part of the area and containing neurons projecting to the amygdala and basal ganglia; the subfascicular area of the mesodiencephalic junction lying medially and caudal to the spf and containing neurons projecting to the raphe´nuclei, the inferior olive, the caudalis subnucleus of the trigeminal complex and the spinal cord. The possibility that the subfascicular area of the mesodiencephalic junction is the effective site for SPA is discussed.

Axonal and transneuronal transport of wheat germ agglutinin demonstrated by immunocytochemistry

Immunocytochemical methods at the light and electron microscopic level were used to examine the anterograde and retrograde transport of wheat germ agglutinin. Following anterograde transport to sensory nerve terminals in the central nervous system, wheat germ agglutinin can be localized to neuronal cell bodies in the area of terminal labeling. The transneuronal transport of wheat germ agglutinin demonstrates the existence of a mechanism whereby axonally transported glycomacromolecules might exert neurotrophic effects on postsynaptic cells.

Differences in the labeling of axons of passage by wheat germ agglutinin after uptake by cut peripheral nerve versus injections within the central nervous system

Injections of a radiolabeled derivative of wheat germ agglutinin (WGA) in the subcortical white matter of the cerebral cortex in mice do not give rise to autoradiographic labeling axons systems coursing through this fiber mass. Exposing the cut-end of mouse tibial nerve to WGA does, however, produce labeling within dorsal root ganglia and the spinal cord. These findings are discussed with consideration for dissimilarity in mode of central versus peripheral administration of the tracer, as well as in the light of potential relative differences in the uptake and transport of WGA and HRP.

Regional cerebral blood flow changes in cortex and basal ganglia during voluntary movements in normal human volunteers

Regional cerebral blood flow changes in cortex and basal ganglia during voluntary movements in normal human volunteers

Uptake and anterograde axonal transport of wheat germ agglutinin from retina to optic tectum in the chick.

The uptake and anterograde axonal transport of 125I-wheat germ agglutinin (WGA) has been investigated in the visual system of the chick. In order to obtain a marker with specific and homogeneous binding properties, the iodinated lectin was affinity purified by passage over an N-acetylglucosamine (NAcGlu)-Sepharose column after iodination. 22 h after vitreal injection of the purified 125I-WGA, radioactive label was found accumulated in the retinoreceptive layers of the contralateral optic tectum. Gel electrophoresis of tectal homogenates revealed that greater than 80% of the retrieved label ran in a band which comigrated with native WGA. In chicks injected with the fraction of the iodinated preparation that failed to bind to the affinity column, there was no evidence of tectal labeling. These findings support the hypothesis that WGA is selectively taken up by chick retinal ganglion cells and transported intact in an anterograde direction to their axon terminals in the contralateral optic tectum. This raises the possibility that constituents of perikaryal membrane, i.e., lectin receptors, are transported in an anterograde direction by chick retinal ganglion cells.

Comparison of effects of stimulation of Deiters' nucleus and medial longitudinal fasciculus on neck, forelimb, and hindlimb motoneurons.

Comparison of effects of stimulation of Deiters' nucleus and medial longitudinal fasciculus on neck, forelimb, and hindlimb motoneurons.

Inhibition of central vestibular neurons from the contralateral labyrinth and its mediating pathway.

Inhibition of central vestibular neurons from the contralateral labyrinth and its mediating pathway.