Expression of pannexin1 in the CNS of adult mouse: cellular localization and effect of 4-aminopyridine-induced seizures.

The expression pattern of pannexin1, a gene coding for a protein that forms gap junction channels, was studied as both mRNA and protein in the CNS of adult mouse. Pannexin1 was widely expressed in the CNS by neuronal cell types but not glial cells, except for Bergmann glial cells of the cerebellar cortex. Cells positive to Ca-binding proteins, principally parvalbumin, but also calbindin and calretinin, as well as glutamate decarboxylase 67 kDa isoform, were pannexin1-positive. Pannexin1 labeling was found in cells which are known to exhibit spontaneous and synchronous discharge, such as neurons of the inferior olivary complex and the reticular thalamic nucleus, and also in neurons whose electrical activity is not coupled with neighboring cells, such as motoneurons of the spinal cord. The analysis of cellular localization showed puncta that surrounded cell bodies (e.g. the pyramidal cells of hippocampus) or restricted areas inside the cell bodies (e.g. the spinal motoneurons). In Bergmann glial cells the staining was present as fine grains that covered a large part of the cellular surface. Pannexin1 stained cells that previous studies have reported as expressing connexin36, another protein forming gap junction channels. Thus, it was possible that these two proteins could be integrated in the same functions. Since connexin36 expression levels change after seizures, we examined the expression of both pannexin1 and connexin36 in cerebral cortex, hippocampus, cerebellum and brain stem at different time intervals (2, 4 and 8 h) after i.p. injection of 4-aminopyridine, which resulted in systemic seizures. The only modification of the expression levels observed in this study concerned the progressive decrement of the connexin36 in the hippocampus, while pannexin1 expression was unchanged. This finding suggested that pannexin1 and connexin36 are involved in different functional roles or that they are expressed in different cell types and that only those expressing the Cx36 are induced to apoptosis by epileptic seizures.

Multiple zonal projections of the nucleus reticularis tegmenti pontis to the cerebellar cortex of the rat.

Compartmentalization (alternating labelled and unlabelled stripes) of mossy fibre terminals was found in the cerebellar cortex after iontophoretic injections of biotinylated dextran amine into discrete regions of the nucleus reticularis tegmenti pontis (NRTP). The zonal pattern was only observed when volumes of nuclear tissue ranging from 4.5 x 106 to 17.66 x 106 microm3 were impregnated. Up to nine compartments (i.e. up to five stripes separated by four interstripes) were found in crus I and in vermal lobule VI. Up to seven compartments (four stripes and three interstripes) were found in crus II; up to five compartments (three stripes and two interstripes) were identified in the lobulus simplex, the paraflocculus and vermal lobules IV, V and VII; up to three compartments (two stripes and one interstripe) were identified in the paramedian lobule and, finally, up to two compartments (one stripe and one interstripe) were identified in the copula pyramidis, in the flocculus and in vermal lobules II, III, VIII and IX. The projections of the NRTP are arranged according to a divergent/convergent projection pattern. From single injections in the NRTP, projections were traced to a set of cortical stripes widely distributed over the cerebellar cortex. The set of stripes labelled from different regions of the NRTP partially overlapped but complete overlap was never found. This finding revealed that the topographic combination of the projections of the NRTP to the cerebellar cortex is specific for each region of the NRTP. Finally, the projections to single cortical areas were arranged according to a pattern of compartmentalization that is specific for each cortical area, independent of the site of injection in the NRTP and of the number of stripes evident in the cortex.

Laterality of the pontocerebellar projections in the rat.

This study aimed to investigate the trajectory of fibres from the pontine nuclei that reach the two sides of the cerebellum. Injections of biotinylated dextran amine (BDA) were made within the basilar pontine nuclei (BPN) and the nucleus reticularis tegmenti pontis (NRTP) in one side of rats with electrolytic injury of the middle cerebellar peduncle (MCP), ipsilateral or contralateral to the side of injection. Fibres were traced from the pontine nuclei (BPN and NRTP) to both sides of the cerebellum passing through the respective MCPs. The study carried out in rats with injury to one peduncle showed projections segregated to the half-side of the cerebellum innervated by the intact peduncle. The laterality observed was confirmed by a retrograde tracer study. In fact, injections of different fluorescent tracers in rats with injury of single MCP showed that in the pontine nuclei only cell bodies stained by the tracer injected in the half-cerebellum ipsilateral to the intact peduncle. Finally, similar injections (i.e. different fluorescent tracers in symmetric areas of the cerebellar cortex) in the cerebellum of intact brain rats showed that BPN and NRTP differ for the laterality of their projections. In fact, 82% of BPN cells project contralaterally and 18% ipsilaterally, whereas 60% of NRTP cells project contralaterally and 40% ipsilaterally. In conclusion, this study showed that the MCPs receive fibres from the pontine nuclei of both sides and project to the ipsilateral half of the cerebellum and that different contingents of projections to the two sides of the cerebellum arise from BPN and NRTP.

Corticonuclear projections of the cerebellum preserve both anteroposterior and mediolateral pairing patterns.

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 biotinylated dextran amine into the cerebellar cortex orthogradely labelled fibre 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 specifically 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.

Multiple zonal projections of the basilar pontine nuclei to the cerebellar cortex of the rat.

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.

Diverging projections of the C2 and D2 olivocorticonuclear cerebellar pathways of the rat.

A divergent mediolateral projection to the cerebellar nuclei of the C2 and the D2 olivocorticonuclear cerebellar pathways was found after segregate injections of a tracer (either WGA-HRP or FR or BDA) in the rostral (D2 area) or caudal side (C2 area) of the rat paraflocculus. The C2 olivary area of the cerebellar cortex sends most of its nuclear projection to the nucleus interpositus posterior (classically perceived as the nuclear target of the C2 olivocorticocerebellar pathway) and a smaller contingent of fibres to the parvocellular region of the nucleus lateralis (classically perceived as the nuclear target of the D2 olivocorticocerebellar pathway). The D2 olivary area of the cerebellar cortex sends most of its nuclear projection to the parvocellular region of the nucleus lateralis (classically perceived as the nuclear target of the D2 olivocorticocerebellar pathway) and a smaller contingent of fibres to the magnocellular region of the nucleus lateralis (classically perceived as the nuclear target of the D1 olivocorticocerebellar pathway). The lateral interaction of the D2 and the C2 olivocerebellar pathways could represent the anatomical substrate for the functional integration of different olivocerebellar compartments.

The projections of the lateral reticular nucleus to the deep cerebellar nuclei. An experimental analysis in the rat.

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 rostral 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.

The projection from the primary motor and somatic sensory cortex to the basilar pontine nuclei. A detailed electrophysiological and anatomical study in the rat.

The projections from the primary motor and somatic sensory cortex onto the basilar pontine grey were studied in Wistar Rats injecting microvolumes of WGA-HRP solution in sites of the motor and sensory cortex electrophysiologically identified. The main results may be summarized as follows. (a) The projections from both the motor and sensory cortex were found as rostrocaudally oriented columns of terminals in the basilar pontine nuclei. The projection from the motor cortex extended to all over the rostrocaudal extension of the basilar pontine nuclei. To a rostrocaudal shift of the pontine projection field correspond a rostrocaudal displacement in the motor area. The projection from the sensory cortex was mainly restricted to the caudal two thirds of the basilar pontine nuclei, though the hindlimb region of the sensory cortex also showed a discrete representation in the rostral third of the basilar pontine nuclei. (b) The terminal fields of the motor and sensory cortex were segregated except those in the caudal pontine level, which come from the projection of the hindlimb cortical regions. (c) Within the terminal fields of the projections from the motor as well as from the sensory cortex a clearcut topographical arrangement was observed between the projections of cortical areas controlling the head, the forelimb and the hindlimb regions. (d) Within the location of these major subdivisions, the representations of individual body segments were overlapped for a little part ("convergent zones"), whereas the greater part of their projection zones was selective of each cortical field ("private zones"). In conclusion, the present study showed that the projections from the motor and sensory cortex to the basilar pontine nuclei are arranged with a very precise somatotopical organization.

The pontocerebellar projection: longitudinal zonal distribution of fibers from discrete regions of the pontine nuclei to vermal and parafloccular cortices in the rat.

A longitudinal parasagittal organization (alternating labeled and unlabeled stripes) of mossy fiber terminals in the paraflocculus and in the vermal lobule VII of the cerebellum was found after small injections (less than 50 nl) of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) into discrete regions of the basilar pontine nuclei (BPN) of rats. Up to three stripes were found within the paraflocculus of both sides, following injections (of about 500 microns in diameter) in either the medial or lateral region of the caudal half of the BPN. Up to five stripes were found in the vermal lobule VII after similar size injections into the rostro-ventral region of the BPN. These results emphasize the possibility that the parasagittal zonal arrangement could be a common pattern of organization shared by climbing and mossy fiber afferents.

Multiple representation in the nucleus lateralis of the cerebellum: an electrophysiologic study in the rat.

The motor organization of the nucleus lateralis (NL) of the rat's cerebellum was investigated by observing the motor effects of electrical microstimulations of the NL. The movements evoked by the NL mainly concerned forelimb and head segments. Only in a few cases were movements of hindlimb segments evoked. Motor effects were obtained according to a precise topographical pattern. This pattern delimited functional zones, or representations, within the NL, each zone being specifically related to a particular segment of the body. A few body segments were activated from single zones only (single representation) whereas some other body segments could be activated from different zones of the NL. Among them, the axio-proximal body segments were activated in a similar way from all sites (multiple representation) whereas the distal body segments were differently activated from the various representation zones (specific representation). The multiple and specific representations were distributed between the 3 cytoarchitectonic subregions of the NL (NLm, DLH and slp) in such a way that the body segments were usually represented only once in each individual NL subregion. Each NL subregion included sets of representations concerning body segments characterized by a topographical continuity (e.g. the different segments of the forelimb in both DLH and slp). Thus, the individual NL subregions may bring into play coordinate plurisegmental muscular activities of the limbs and/or of the head. The NLm controls movements of all the segments of the head and those of axio-proximal segments of both limbs. The DLH particularly controls movements of the head, including both the proximal (neck) and the oral regions. To a lesser degree, DLH controls movements of the various segments of the forelimb, including synchronous flexion of all the digits. The slp is specifically involved in the control of motor activities of: i) the proximal segment of the head (rotation of the neck) as well as its distal segments (displacement of individual vibrissae, rotation of the ear pinna) and ii) the various segments of the forelimb including individual digits. Functionally, the proximal segments would be concerned in the spatial displacement of the limbs or of the head whereas the distal segments would be involved in the realization of precise and discrete movements related to specific functions of the distal segments concerned. The 3 subregions of the NL may be concerned in different motor functions.(ABSTRACT TRUNCATED AT 400 WORDS)

[Motor organization of the lateral cerebellar nucleus of the rat]. / Organizzazione motoria del nucleo cerebellare laterale di ratto.

The motor organization of the nucleus lateralis (NL) of the cerebellum of the rat was investigated by studying the motor effects following the electrical microstimulation. The movements evoked by the NL stimulation concerned prevalently the forelimb and the head segments. The movements of the hindlimb segments were evoked in only few cases. The NL is organized as a mosaic of zones without, or at least very little overlap. The various body segments are differently represented in the NL. Some of them are once represented (single representations). In other cases, the same movements were evoked by different NL regions (multiple representations). Finally, in a last lot of cases, various representations concerned the same body regions but from each representation a different type of movement was evoked (specific representations, i.e. displacement of an individual digit and flexion of all digits together). The topographical distribution of the representations in the NL cytological regions (magnicellularis, NLm; dorsolateral hump, DLH; subnucleus lateralis parvocellularis, slp) suggests the idea that each of them may be concerned in a specific motor activity: the NLm would control the position of the body, or of part of it, in the space; the DLH would be concerned in the oral (prevalently) and in the forelimb motor activity; the slp would be concerned in the exploration of the environment as well as in skilled movements of the distalmost forelimb segments.

Functional organization of the direct and indirect projection via the reticularis thalami nuclear complex from the motor cortex to the thalamic nucleus ventralis lateralis.

The projection systems which arise from the motor cortex to reach the nucleus ventralis lateralis (VL) were investigated in the rat. They included a direct as well as an indirect projection via the reticularis thalami nuclear complex (RT). The investigation was performed in two steps: i) the former concerned the projection to the VL as well as to the RT from individual cortical foci electrophysiologically identified by the motor effects evoked by electrical stimulation; the second step concerned the projection from the RT to functionally defined regions of the VL. The direct projection from the motor cortex to the VL is somatotopically arranged. The projection reciprocates the fiber system directed from the VL to the motor cortex. Thus cortical zones controlling the motor activity of the proximal segments of the limbs project onto the regions of the VL that project back to these same cortical areas. With regard to cortical zones controlling the motor activity of the distal segments of the limbs, they not only project to the region of the VL specifically related to them, but also to the region of the VL associated with the cortical areas responsible for movements of the proximal parts of the same limb. In that case fiber terminals were more dense in the VL region controlling the proximal segment than in the region controlling the distal segment of the same limb. This organization suggests that proximal adjustments may be automatically provided by the motor activity of the distal segments of the same limb. The motor cortex projects to the rostral region of the RT with a precise topographical organization. In particular, the projection shows a dorsoventral organization in the RT in relation to the caudorostral body representation in the motor cortex. The projection which arises from the rostral region of the RT also reaches the VL with a topographical arrangement. It discloses a rostrocaudal organization in the VL in relation to a dorsoventral displacement in the RT. Comparing the projection from the motor cortex to the RT and that from this nuclear complex to the VL it was shown that the regions of the VL and their receptive cortical areas were associated with the same regions of the RT. It was therefore concluded that the motor cortical projection to the VL relayed by the RT is somatotopically organized. In both direct and relayed pathways the projections from "hind-" and "forelimb" motor area are segregated, whereas the "head" projection overlaps, at least partially, the "forelimb" terminal field.(ABSTRACT TRUNCATED AT 400 WORDS)

Neocerebellar control of the motor activity: experimental analysis in the rat. Comparative aspects.

The results collected by electrical microstimulation of the nucleus lateralis of the cerebellum in anaesthetized rats may be summarized as follows. The stimulations evoked motor effects in head and forelimb principally whereas hindlimb was only occasionally involved. The movements were prevalently segregated to only one joint (simple movements), in a lesser degree they involved two or three segments (complex movements). Simple and complex movements were apparently distributed in the nuclear mass without topographical segregation or preferentiality. The electromyographic records suggest that the neocerebellar movements are of synergistic nature. A somatotopical organization was evidenced within the nucleus lateralis: 3 specific functional regions were identified in the caudorostral nuclear extension. They concern the forelimb (caudally), head (centrally) and hindlimb (rostrally). This somatotopical organization persisted unmodified following elimination of either the cerebral motor cortex alone or in addition to that of the red nucleus. The nuclear subdivisions of the cerebellar nucleus lateralis showed functional differences: (1) the dorsolateral hump of Goodman et al. was principally involved in lip movements; (2) the subnucleus lateralis parvocellularis elicited movements of single vibrissae, neck and medio-distal segments of the forelimb, prevalently; (3) the magnocellular subdivision essentially controlled both limbs with large prevalence for their medio-proximal segments. To identify the functional role of the different descending pathways which relay the neocerebellum to the cord, the motor effects evoked in intact rats were compared with those elicited in rats submitted to cortical ablation and/or to lesion of the red nucleus region. The integrity of the cerebral cortex was essential only for distalmost forelimb motor activities. After lesion of the rubral region (which concomitantly eliminates corticospinal output), the stimulation of the nucleus lateralis evoked motor effects of the proximo-axial segments prevalently with intensity thresholds increased above two-fold those obtained in intact/decorticated rats. The movements elicited in rats with injury of the red nucleus region, including the ascending fibers of the brachium conjunctivum, are presumably mediated to the spinal cord through the reticulospinal pathway. The proportion of simple and complex movements decreased and increased respectively after cortical ablation and further on after injury of the red nucleus region. The discussion on the motor effects elicited in rats by the neocerebellum focussed on the possible role of 3 descending pathways.(ABSTRACT TRUNCATED AT 400 WORDS)

Electrophysiologic properties and nature of ventrolateral thalamic nucleus neurons reactive to converging inputs of paleo- and neocerebellar origin.

Acute experiments were carried out in chloralose-anesthetized, curarized, and artificially ventilated cats to investigate the consistency and functional characteristics of converging cerebellar nuclear (fastigial, interpositus, dentate nuclei) inputs to single neurons of the ventrolateral thalamic nucleus, and the nature (thalamocortical relay or interneuronal) of its convergent neuronal population responsive to stimulation of the cerebellar nuclei. From unitary analysis of both extra- and juxtacellular recordings, we conclude that convergence of paleo- and neocerebellar impulses on thalamic ventrolateral neurons occurs widely, and that both excitatory (mono- and polysynaptic) and inhibitory (di- and polysynaptic) effects are induced on the same neurons by cerebellar nuclei stimulation; these effects concern about 40% of the thalamic ventrolateral neuronal population tested using the extracellular recording technique and about 75% of the ventrolateral nucleus neurons tested using the juxtacellular recording; activation of neocerebellar nuclear outputs generates mainly excitatory and excitatory-inhibitory response patterns, whereas activation of the paleocerebellar nuclear outputs evokes predominantly inhibitory and excitatory-inhibitory response patterns; the convergent paleo- neocerebellar neurons are found commonly in the more anterior ventrolateral nucleus stereotaxic planes; and from the results obtained by stimulation of the somatomotor cortical areas, a large proportion of the ventrolateral nucleus convergent units consists of thalamocortical relay cells. The results have implications for a possible integration between posture and voluntary movements at the level of the thalamic relay nucleus of the cerebellar-cortical pathway, and an interaction between central feedback and peripheral feedback in the programming, execution, and correction of voluntary movements.

An autoradiographic study of the cerebellopontine projections from the interposed and lateral cerebellar nuclei in the rat.

The projections from the cerebellar lateral and interposed nuclei onto the basilar pontine gray and nucleus reticularis tegmenti pontis (NRTP) have been studied in the rat by the use of the autoradiographic technique. Projections from both nuclei are mainly contralateral. Fibers from the lateral nucleus cover most of the NRTP, except its medial, parvocellular portion. In the pontine gray proper, fibers from the lateral nucleus are distributed to three rostrocaudally oriented columns: (i) in the medial nucleus, (ii) in the ventral nucleus, and (iii) in the dorsolateral and lateral nuclei. The projection is topographically arranged, so that caudal parts of the lateral cerebellar nucleus tend to project to more rostral regions than rostral parts of the lateral nucleus. The interposed nucleus gives rise to a sparser projection, apparently limited to the ventral NRTP and immediate peripeduncular zones. The functional implications of these results are discussed, with particular emphasis on the convergence of corticopontine afferents to the pontine regions involved, and on the reciprocal pontocerebellar pathways from these same regions.

Pyramidal influences on ventral thalamic nuclei in the cat.

In pericruciate cortex-ablated 'pyramidal cats', discharge changes in single neurons of ventral thalamic nuclei were studied, following stimulation of ipsilateral medullary (MPT) and contralateral cervical (CPT) pyramidal tract. It was seen that cells in ventrolateral nucleus, ventroanterior nucleus and ventromedial nucleus were not significantly (2.2%) modified by impulses coming from MPT and CPT. Conversely, a very high percentage (58.8%) of cells in ventrobasal complex (VB) responded to MPT stimulation (64.4% in ventroposterolateral nucleus, VPL, and 40.7% in ventroposteromedial nucleus, VPM). A considerable number (34.8%) of VPL cells responsive to MPT, were influenced by CPT, while none of the cells in VPM were. The most frequent effect observed in VB neurons, on MPT and CPT stimulation, was excitation followed by depression of discharge.

[Ponto-medullary projections to the spinal cord: a quantitative study in the cat]. / Proiezioni bulbo-pontine dirette al midollo spinale: studio quantitativo, nel gatto.

The purpose of this research has been to study quantitatively the ponto-medullary projections to the lateral and ventral funiculi in both cervical (C3) and thoracic (Th8) levels. The method consisted in the partial interruption of the spinal cord, sparing one funiculus in which 5-30 microliter of HRP 30% solution was injected at about 1 cm caudally. 19 cats were utilized, 12 for cervical (6 for lateral and 6 for ventral funiculus) and 7 for lumbar injection (3 for lateral and 4 for ventral funiculus). The structures which project to both funiculi of spinal cord (RM, RL, Poo, PR at Th8 level; RM, RL, Poo at C3 level) could exert integrative effects on the proximal and distal segments of the limbs. The structures which project only to FV (VL and Poc at Th8 level; VL, VIN and Poc at C3 level) or to FL (LSC at Th8; PR at C3) could be implied in motor control of only the proximal or distal regions.

An autoradiographic study of the cerebellopontine projections in the rat. I. Projections from the medial cerebellar nucleus.

The medial cerebellar nucleus of the rat is shown by the autoradiographic technique to project to both the contralateral nucleus reticularis tegmenti pontis and the pontine nuclei proper. The former projection is more concentrated in the medial--parvocellular --region. In the pontine gray, the bulk of the projection concerns the dorsal aspect of the medial nucleus. Rostral parts of the medial cerebellar nucleus project to caudal pontine levels whereas caudal parts seem to project throughout the rostrocaudal extent of the basilar pons.