Laterality of the pontocerebellar projections in the rat (original) (raw)
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The Journal of Comparative Neurology, 2002
AB ST R ACT T his stu dy show ed the precise projection pattern of the basilar pontine nu clei (B PN) and the nu cleu s reticu laris tegmenti pontis (NR T P) to the cerebellar nu clei (CN), as w ell as the different anatomic featu res of B PN and NR T P projections. T he staining of B PN or NR T P w ith biotinylated dextran labeled projection fibers to complementary topographic areas in the CN. In fact, B PN principally project to a rostrocau dally oriented colu mn of the nu cleu s lateralis (NL ), w hich at the midcentral lev el shifts to the laterov entral part of the nu cleu s, as w ell as to the cau dolateral part of the nu cleu s interpositu s posterioris. T he NR T P projects to a rostrocau dal colu mn of the NL , w hich at the midcentral lev el shifts medially, as w ell as to the nu cleu s interpositalis and to the cau dal part of the nu cleu s medialis. B PN axons in the CN u su ally branch into short collaterals of simple morphology that inv olv e small terminal areas, w hereas NR T P axons branch into longer collaterals of complex morphology inv olv ing terminal areas of different sizes. E ach site of injection is at the origin of a set of terminal areas in the CN. T he set of projections from different B PN or NR T P areas w ere partially, bu t nev er completely, ov erlapping. T hu s, the set of terminal areas in the CN w as specific for each area of both B PN and NR T P. Injection of tetramethyl-rhodamine-dextran-amine into the CN stained cell bodies of B PN and NR T P w ith different repartition on the tw o sides. T he stu dy show ed that CN are innerv ated by the contralateral B PN and not v ery mu ch by the ipsilateral B PN, w hereas they are innerv ated by NR T P bilaterally, ev en if w ith a contralateral prev alence. In conclu sion, this stu dy su pports the hypothesis that both B PN and NR T P are concerned in the central program for sk illed mov ements, ev en if they are probably inv olv ed in different fu nctional roles. I ndex ing terms: cerebellum; BPN; NRTP; neuroanatomy ; rat T he cerebellu m (CB L ) is reached by mossy fibers from v ariou s brain regions, principally from the basilar pontine nu clei (B PN) and the nu cleu s reticu lar tegmenti pontis (NR T P). T he NR T P w as long considered together w ith the B PN. Inv estigations hav e show n that the NR T P is a specialized nu cleu s of the pontine reticu lar formation (Newman and G insberg, 1992) and that it differs both in ontogeny and in the afferent connectiv ity pattern from the B PN. In fact, w ithin the cortical limits, most afferents to the B PN of rat arise from the entire ipsilateral cortex (L egg et al., 198 9) and principally from sensory (particu larly v isu al and au ditory) and associativ e cortical areas (B rodal and B jaalie, 1992; cf. also Paxinos, 1995, p. 27 8 ), w hereas afferent inpu ts to the NR T P stem from the cingu lar (T origoe et al., 198 6) and, in particu lar, the motor cortices (B rodal, 198 0). L ik e the tegmentu m, how ev er, the NR T P appears to receiv e bilat-eral cortical inpu ts (B rodal, 198 0; L eichnetz et al., 198 4 ) rather than the predominantly ipsilateral inpu ts of the basilar pons . M oreov er, the cortical afferent inpu ts to the NR T P do not generally occu r in the separate w ell-restricted grou ps that are so conspicu ou s in the pontine nu clei in the same sections (B rodal, 198 0). B ecau se the NR T P and B PN differ in ontogenesis and in G rant sponsor: M inistry of E du cation and Scientific R esearch (M U R ST ). * Correspondence to: Federico Cicirata, Dipartimento di Scienze Fisiologiche, V iale A. Doria 6, © 20 0 2 W I LEY-LI S S , I NC.
European Journal of Neuroscience, 1996
The projections of the lateral reticular nucleus (LRN) to the cerebellar nuclei were studied using the retrograde axonal transport of tetramethyl rhodamine dextran amine (10% solution in 0.01 M neutral phosphate buffer) in 19 adult Wistar strain rats. The cerebellar nuclei receive topographically organized projections from the LRN. The projections are bilateral with an ipsilateral predominance and they are symmetrical. The contralateral component is progressively larger for projections to the nuclei interpositalis, to the nucleus lateralis and to the nucleus medialis. The projections to the various cerebellar nuclei arise from rostrocaudally oriented columns of neurons located in different (partly overlapping) areas of the magnocellular division of the LRN. The nucleus lateralis receives terminals from the dorsomedial area (mainly from the rostra1 level of the LRN), the nuclei interpositalis from the dorsolateral area (mainly from the central level) and the nucleus medialis from the intermedioventral area (mainly from the caudal level). Afferent fibres from the small subtrigeminal division were traced to the three cerebellar nuclei and from the parvocellular division to the nuclei interpositalis and medialis. The density of the projections from the LRN to the nuclei interpositalis increases progressively with the shift of the terminal field from the rostrolateral to the caudomedial part of the nucleus. The projections to the nucleus lateralis reach principally the dorsolateral hump, whereas only a few neurons project to the other divisions (parvo-and magnocellular). The projections to the various regions of the nucleus medialis show different densities. The highest density was found for projections to the caudal part, in particular to the dorsolateral protuberance and to the ventrolateral area of the middle division. Conversely, a low density of projections was found for the other areas of the middle division. The regions of the magnocellular division of the LRN which project to the nuclei lateralis (and are thus related to the cerebral cortex), interpositalis (related to the red nucleus) and medialis (related to the spinal cord) also receive afferent terminals from the cerebral cortex, the red nucleus and the spinal cord respectively, in addition to various afferent inputs. Thus, each of these areas is apparently concerned with integrating some spinal and supraspinal information in reverberating circuits.
Multiple zonal projections of the basilar pontine nuclei to the cerebellar cortex of the rat
Journal of comparative neurology, 2001
This study revealed a sagittal zonal pattern of projections to the cerebellar cortex after hydraulic or iontophoretic injections of anterograde tracers (tritiated leucine, wheat germ agglutinin-horseradish peroxidase, or biotinylated dextrane amine) in the basilar pontine nuclei of Wistar rats. The zonal pattern of projection was observed only after injections of small size, whereas large injections labeled diffusely wide areas of the cerebellar cortex, masking the zonal projection because the fusion of contiguous stripes. Diverging projections to discrete sets of sagittal stripes in the two sides of the cerebellar cortex arose from single injections. The stripes of fiber terminals were sharply delimited on both sides by areas, interstripes, either virtually void of labeling or with a much lower density of labeling. Thus, the areas of the cerebellar cortex were parceled in sets of sagittal compartments, stripes and interstripes, by the pontine projections. Up to five compartments (three stripes and two interstripes) were observed in the paraflocculus, in the copula pyramidis, and in vermal lobule IX. Up to nine compartments (five stripes and four interstripes) were found in the crus I, the lobulus simplex, the paramedian lobule, and vermal lobules VI-VIII. Up to seven compartments (four stripes and three interstripes) were found in the crus II. Single injections into the basilar pontine nuclei usually labeled symmetric areas of the cerebellar cortex, which, in some cases, showed similar number of stripes. When this was not the case, the stripes were usually more numerous in the contralateral than in the ipsilateral side. All areas of the cerebellar cortex were projected upon, with zonation patterns from different regions of the basilar pontine nuclei. The projections of the basilar pontine nuclei to the cerebellar cortex were arranged according to a fixed pattern specific for each cortical area, independently of the number of stripes labeled within. The mean width of the stripes visualized in the single cortical areas of different rats was similar, despite the different size of the injections. The length of the stripes ranged widely in the various areas of different rats. The data collected in this study are consistent with the idea that all the mossy afferents to the cerebellar cortex are arranged with a zonal pattern.
European Journal of Neuroscience, 2001
The aim of the present study was to establish whether a diverging arrangement of the corticonuclear cerebellar projections exists and, if so, what relation it has with the inferior olivary complex. Iontophoretic injections of a 1 : 1 mixture of tetramethylrhodamine dextran amine and byotinilated dextran amine into the cerebellar cortex orthogradely labelled ®bre terminals in the cerebellar nuclei and retrogradely labelled cell bodies in the inferior olivary complex. The injections were into A, B, C2, C3, D1 and D2 bands. These injections showed diverging projections to the cerebellar nuclei, with`primary projections' directed to the nuclear region previously reported to be speci®cally connected with the injected band and`secondary projections' directed to other nuclear regions. Secondary projections from the A, C2 and C3 bands diverged to nuclear regions primarily controlled by cortical bands lateral to those injected. Secondary projections from the D1, and D2 bands diverged to nuclear regions primarily controlled by cortical bands medial to those injected. Moreover, injections distributed along the D1 and D2 bands showed similar sets of nuclear targets, while those distributed along the A, C2 and C3 bands showed two sets of nuclear targets in relation to the anteroposterior location of the injected area within these bands. The cortical areas that projected to the same set of nuclear targets were innervated from single olivary regions, while those that projected to different sets of nuclear targets were innervated from different subsets of single regions of the inferior olive. The results suggest that the olivary bands of the cerebellar cortex project to the cerebellar nuclei with a diverging pattern that is organized in both the mediolateral and the anteroposterior axes.
Reticulocerebellar projections to the anterior and posterior lobes of the rat cerebellum
Neuroscience Letters, 2001
By using retrograde double-labeling techniques, we analyzed the topography of projections from the lateral reticular nucleus (LRN) to the anterior and posterior lobes of the cerebellum, with the aim to investigate whether LRN projections to the two lobes come from different neurons or from branching axons of the same cells. We observed that about 4/5 of afferents the cerebellar cortex come from the ipsilateral LRN and about 1/5 from the contralateral nucleus. Furthermore, magnocellular division of LRN projects mainly to the anterior lobe, whereas parvicellular part primarily to the posterior lobe. The double-labelled cells were very numerous (about 1/3) and were located throughout the LRN, with the higher incidence in the magnocellular division and the lower in the subtrigeminal part.
Cerebellar connections to the rostral reticular nucleus of the thalamus in the rat
Journal of Anatomy, 2002
We studied the cerebellar connections to the reticular nucleus thalamus (RNT) by means of retrograde axonal transport of horseradish peroxidase (HRP) in the rat. Specific HRP pressure injections to the rostral RNT (1.6-1.8 mm caudal to bregma) resulted in retrograde labelling of neurones in the cerebellar nuclei. The rostral RNT showed specific topographical organization of its cerebellar connections. Microinjections into the rostral RNT, 1.6 mm caudal to bregma, produced numerous HRP-labelled neurones within the anterior interposed (emboliform nucleus) and scarce HRP-labelled neurones within the lateral (dentate nucleus) cerebellar nuclei, whereas injections into the rostral RNT, 1.8 mm caudal to bregma, produced numerous HRP-labelled neurones within the posterior interposed (globose nucleus) and scarce lightly HRP-labelled neurones within the lateral (dentate nucleus) cerebellar nuclei. Cerebellar connections with the rostral RNT were exclusively ipsilateral to the injection site. No HRP-labelled cells were detected in the medial (fastigial nucleus) cerebellar nucleus. The cerebellar connections reach the RNT via the superior cerebellar peduncle. By contrast, HRP injections into the anterior, posterior interposed and lateral cerebellar nuclei produced no labelled cells within the RNT. This study demonstrates the existence of direct cerebello-RNT but not RNT-cerebellar connections. The presence of the cerebello-RNT connections introduces a new route through which the cerebellum may influence RNT and thus cerebral cortical activity.
Anatomy and Embryology, 1982
The projection from the lateral reticular nucleus (LRN) to the cerebellar cortex was studied in the rat by utilizing the retrograde transport of horseradish peroxidase (HRP). In order to study the topographic features of this projection, small amounts of HRP were injected into various sites in the cerebellar cortex. The results demonstrated that the caudal lobules of the anterior lobe vermis tend to receive afferents from the medial LRN and the rostral lobules of the vermis receive afferents from more laterally situated cells. Lobules IV and V receive inputs primarily from the magnocellular division of the LRN of both the ventromedial and dorsolateral parts of the LRN, while lobules II and III receive inputs mainly from cells which lie in the border area between the parvocellular and magnocellular division of the ventromedial part. Following injections within various areas of the posterior lobe vermis, the results indicated that lobule VIII receives the most abundant projection from the LRN and that the cells of origin are present within the parvocellular and the adjacent part of the magnocellular division throughout the rostrocaudal extent of the LRN. Following injections within lobules VI and VII, few labelled cells were found and they tended to lie within the rostral two-thirds of the magnocellular division. Little or no projection from the LRN to lobule IX was evident. The hemispheres were found to receive a modest projection from the dorsal aspect of the LRN. The projection to lobulus simplex originates mainly from the caudal two-thirds of the magnocellular division, while the projection to the ansiform and paramedian lobules originates mainly from the dorsal aspect of the rostral two-thirds of the magnocellular division. Finally, there appears to be extensive overlapping of the origins of all three projections to the cerebellar cortex studied, and this occurs within the central area of the magnocellular division throughout the rostrocaudal extent of the LRN.
European Journal of Neuroscience, 1995
The extent to which the cells of origin of the cerebellar nucleocortical pathway are immunopositive for y-aminobutyric acid (GABA) was investigated in four cats using retrograde labelling of nucleocortical neurons in combination with immunocytochemistry. Neurons were retrogradely labelled by injection of fluorescent (coumarin)-tagged latex microspheres into the c2 zone in the rostral part of the paramedian lobule. The zone was identified electrophysiologically by the characteristics of the climbing fibre responses evoked on the cerebellar surface by percutaneous stimulation applied to the left and right forepaws in pentobarbitoneanaesthetized animals. Sections of the cerebellum containing the retrogradely labelled neurons were processed for GABA immunocytochemistty using a fluorescent (rhodamine)-tagged immunoglobulin. When viewed with epifluorescence microscopy and appropriate filter blocks the retrogradely labelled nucleocortical neurons could be visualized in the same sections as the GABA-immunopositive neurons. Almost all of a total of 254 labelled nucleocortical neurons were located in nucleus interpositus posterior, where a total of 71 1 GABAergic neurons were also found. None of these cells contained coumarin-tagged beads and displayed immunoreactivity for GABA (i.e. none was double-labelled). When compared by area of their cell body, the nucleocortical and GABAimmunopositive neurons appeared to form two partially overlapping populations. The mean cell area of the nucleocortical neurons was 620 ? 233 pm2 (SD), whereas the GABA-immunopositive neurons were much smaller, with a mean cell area of 220 z 115 pm2. The results suggest that GABA does not play a major role in the nucleocortical pathway to the c2 zone of the rostral paramedian lobule of the cat cerebellum.