Anterior Lobe Vermis Research Articles

Neuron specific α-adrenergic receptor expression in human cerebellum: Implications for emerging cerebellar roles in neurologic disease

Recent data suggest novel functional roles for cerebellar involvement in a number of neurologic diseases. Function of cerebellar neurons is known to be modulated by norepinephrine and adrenergic receptors. The distribution of adrenergic receptor subtypes has been described in experimental animals, but corroboration of such studies in the human cerebellum, necessary for drug treatment, is still lacking. In the present work we studied cell-specific localizations of α 1 adrenergic receptor subtype mRNA (α 1a, α 1b, α 1d), and α 2 adrenergic receptor subtype mRNA (α 2a, α 2b, α 2c) by in situ hybridization on cryostat sections of human cerebellum (cortical layers and dentate nucleus). We observed unique neuron-specific α 1 adrenergic receptor and α 2 adrenergic receptor subtype distribution in human cerebellum. The cerebellar cortex expresses mRNA encoding all six α adrenergic receptor subtypes, whereas dentate nucleus neurons express all subtype mRNAs, except α 2a adrenergic receptor mRNA. All Purkinje cells label strongly for α 2a and α 2b adrenergic receptor mRNA. Additionally, Purkinje cells of the anterior lobe vermis (lobules I to V) and uvula/tonsil (lobules IX/HIX) express α 1a and α 2c subtypes, and Purkinje cells in the ansiform lobule (lobule HVII) and uvula/tonsil express α 1b and α 2c adrenergic receptor subtypes. Basket cells show a strong signal for α 1a, moderate signal for α 2a and light label for α 2b adrenergic receptor mRNA. In stellate cells, besides a strong label of α 2a adrenergic receptor mRNA in all and moderate label of α 2b message in select stellate cells, the inner stellate cells are also moderately positive for α 1b adrenergic receptor mRNA. Granule and Golgi cells express high levels of α 2a and α 2b adrenergic receptor mRNAs. These data contribute new information regarding specific location of adrenergic receptor subtypes in human cerebellar neurons. We discuss our observations in terms of possible modulatory roles of adrenergic receptor subtypes in cerebellar neurons responding to sensory and autonomic input signals, and review species differences in cerebellar adrenergic receptor expression.

Expression of the immunoglobulin superfamily neuroplastin adhesion molecules in adult and developing mouse cerebellum and their localisation to parasagittal stripes.

Neuroplastin (np) 55 and 65 are immunoglobulin superfamily members that arise by alternative splicing of the same gene and have been implicated in long-term activity-dependent synaptic plasticity. Both biochemical and immunocytochemical data suggest that np55 is the predominant isoform (>95% of total neuroplastin) in cerebellum. Neuroplastin immunoreactivity is concentrated in the molecular layer and synaptic glomeruli in the granule cell layer. Expression in the molecular layer appears to be postsynaptic. First, neuroplastin is associated with Purkinje cell dendrites in two mouse granuloprival cerebellar mutants, disabled and cerebellar deficient folia. Second, in an acid sphingomyelinase knockout mouse with widespread protein trafficking defects, neuroplastin accumulates in the Purkinje cell somata. Finally, primary cerebellar cultures show neuroplastin expression in Purkinje cell dendrites and somata lacking normal histotypic organization and synaptic connections, and high-magnification views indicate a preferential association with dendritic spines. In the molecular layer, differences in neuroplastin expression levels present as a parasagittal array of stripes that alternates with that revealed by the expression of another compartmentation antigen, zebrin II/aldolase c. Neuroplastin immunoreactivity is first detected weakly at postnatal day 3 (P3) in the anterior lobe vermis. By P5, parasagittal stripes are already apparent in the immature molecular layer. At this stage, punctate deposits are also localised at the perimeter of the Purkinje cell perikarya; these are no longer detected by P15. The data suggest a role for neuroplastins in the development and maintenance of normal synaptic connections in the cerebellum.

Immunohistochemistry of Voltage-Gated Calcium Channel alpha1B Subunit in Mouse Cerebellum

Secretion of neurotransmitters is initiated by voltage-gated calcium influx through presynaptic, voltage- gated N-type calcium channels. However, little is known about their cellular distribution in the mouse cerebellum. In the cerebellum, alpha1B immunoreactivity is found mainly on the cell bodies of all Purkinje cells. In addition, the immunoreactivity was detected on a subset of Purkinje cell dendrites, clustered to form a parasagittal array of bands. In the anterior lobe vermis, immunoreactive Purkinje cell dendrites form narrow stripes separated by broad bands of unstained dendrites. Moving caudally through the vermis, these stripes become thicker as a larger fraction of the Purkinje cell dendrites become immunoreactive. This localization study of the alpha1B pore-forming subunits in mouse cerebellum may guide future investigations of the role of calcium channels in neurological pathways.

Compartmental organization of Purkinje cells in the mature and developing mouse cerebellum as revealed by an olfactory marker protein-lacZ transgene.

In a line of transgenic mice (HpY-1), the pattern of expression of an olfactory marker protein (OMP)-lacZ fusion gene was analyzed in the cerebellum, where, in adult mice, OMP-lacZ was expressed primarily in Purkinje cells (PCs) of the posterior lobe. The transgene-expressing PCs were organized in parasagittal bands, with a boundary of expression roughly corresponding to the primary fissure that separates the cerebellum into anterior and posterior compartments. The regional expression of the lacZ gene was also analyzed during embryonic and postnatal development of the cerebellum. Within the cerebellum-isthmus region, transgene expression first was detected at embryonic day 13.5 (E13.5) in a cluster of postmitotic cells. By E14.5, lacZ was also expressed by a subpopulation of migrating PCs in the postisthmal and lateral cerebellar primordium, and, by E16.5, transgene-positive PCs formed caudally four sagittal bands symmetric to the medial embryonic fissure. The caudal pattern was retained in postnatal cerebella, where, by postnatal day 0 (P0), transgene-positive PCs in vermal lobules VIII and IX appeared to be organized in two prominent parasagittal compartments on either side of a negative midline band. In early postnatal animals, the transgene was expressed transiently in the anterior lobe vermis. Hence, from P5 onward, transgene expression appeared mostly restricted to the posterior lobe, where it followed a caudal-to-rostral gradient. In the paraflocculus, transgene-expressing PCs were confined to the rostrodorsal portion. The results indicate that the anterior and posterior cerebellar lobes are regulated by distinct ontogenetic programs, and PCs of functionally distinct cerebellar regions express the transgene differentially. Furthermore, the data suggest that ectopic expression of OMP-lacZ in the cerebellum is under the control of regulatory elements that provide positional information for the regional specification of PC subsets.

Compartmental organization of Purkinje cells in the mature and developing mouse cerebellum as revealed by an olfactory marker protein-lacZ transgene

In a line of transgenic mice (HpY-1), the pattern of expression of an olfactory marker protein (OMP)-lacZ fusion gene was analyzed in the cerebellum, where, in adult mice, OMP-lacZ was expressed primarily in Purkinje cells (PCs) of the posterior lobe. The transgene-expressing PCs were organized in parasagittal bands, with a boundary of expression roughly corresponding to the primary fissure that separates the cerebellum into anterior and posterior compartments. The regional expression of the lacZ gene was also analyzed during embryonic and postnatal development of the cerebellum. Within the cerebellum-isthmus region, transgene expression first was detected at embryonic day 13.5 (E13.5) in a cluster of postmitotic cells. By E14.5, lacZ was also expressed by a subpopulation of migrating PCs in the postisthmal and lateral cerebellar primordium, and, by E16.5, transgene-positive PCs formed caudally four sagittal bands symmetric to the medial embryonic fissure. The caudal pattern was retained in postnatal cerebella, where, by postnatal day 0 (P0), transgene-positive PCs in vermal lobules VIII and IX appeared to be organized in two prominent parasagittal compartments on either side of a negative midline band. In early postnatal animals, the transgene was expressed transiently in the anterior lobe vermis. Hence, from P5 onward, transgene expression appeared mostly restricted to the posterior lobe, where it followed a caudal-to-rostral gradient. In the paraflocculus, transgene-expressing PCs were confined to the rostrodorsal portion. The results indicate that the anterior and posterior cerebellar lobes are regulated by distinct ontogenetic programs, and PCs of functionally distinct cerebellar regions express the transgene differentially. Furthermore, the data suggest that ectopic expression of OMP-lacZ in the cerebellum is under the control of regulatory elements that provide positional information for the regional specification of PC subsets. J. Comp. Neurol. 404:97–113, 1999. © 1999 Wiley-Liss, Inc.

Blebs in the mouse cerebellar granular layer as a sign of structural inhomogeneity. 1. Anterior lobe vermis.

The cerebellum is a modular structure. However, the size of the fundamental compartments is uncertain, with anatomical methods showing a parasagittal band arrangement but electrophysiological mapping suggesting a finer subdivision into microzones and patches. A new anatomical way to demonstrate compartmentation is described. The cerebellum is fixed by perfusion with 70% ethanol, paraffin-embedded and sectioned. When the sections are rehydrated the granular layer pleats into an elaborate array of blebs. These blebs are seen in both transverse and sagittal sections, found in all lobules of both the vermis and the hemispheres, symmetrical about the midline, reproducible between neighboring sections and between individuals, and bear a constant relationship to the Purkinje cell bands as revealed by zebrin II immunocytochemistry. The data suggest that the granular layer of the adult mouse cerebellum is divided into several thousand modules. These modules may reflect the mossy fiber topography, and may be the anatomical equivalents of the tactile receptive field patches. Such a profound compartmentation has important implication for theories of cerebellar structure and development.

Developing mossy fiber terminal fields in the rat cerebellar cortex may segregate because of Purkinje cell compartmentation and not competition.

Many mossy fiber afferent projections to the rat cerebellar cortex terminate in parasagittal bands. In particular, the anterior lobe vermis of the cerebellum contains alternating bands of mossy fibers from the spinal cord and external cuneate nuclei. The cerebellar cortical efferents, the Purkinje cells, are also organized in parasagittal bands. These can be revealed by immunochemical staining for the antigen zebrin II, which is selectively expressed by bands of Purkinje cells. In some cases, the boundaries between mossy fiber terminal fields align with identified transitions between zebrin+/- sets of Purkinje cells, whereas others are located within apparently homogeneous Purkinje cell compartments. Two theories can explain the terminal-field topography: In one view, mossy fiber terminals segregate during development, because growth cones from different sources compete for common territory. Alternatively, mossy fiber growth cones directly recognize chemically distinct target territories, and activity-dependent mechanisms play only minor roles. To explore these issues, two sets of experiments were performed. First, the terminal-field map of the neonatal spinocerebellar projection was compared to the Purkinje cell compartmentation as revealed by anticalbindin immunocytochemistry. Second, subsets of spinocerebellar mossy fiber afferents were ablated early in postnatal development, and the consequences for the neighboring cuneocerebellar terminal fields were mapped in the adult with reference to the zebrin II+/- compartments. These experiments revealed no evidence that competitive interactions constrain the mossy fiber terminal-field distribution but, rather, suggest that the organization of the mossy fiber projections follows the compartmentation of the Purkinje cells.

Cholinergic Innervation of the Cerebellum of the Rat by Secondary Vestibular Afferents

The cholinergic innervation of the cerebellar cortex of the rat was studied by immunohistochemical localization of choline acetyltransferase, radiochemical measurement of ChAT activity, and double labeling of ChAT-positive neurons with HRP injected into the cerebellum. ChAT immunohistochemistry revealed large mossy fiber rosettes as well as finely beaded terminals with different morphological characterization, laminar distribution within the cerebellar cortex, and regional differences within the cerebellum. Large "grapelike" ChAT-positive mossy fiber rosettes that were distributed primarily in the granule cell layer were concentrated, but not exclusively located, in three separate regions of the cerebellum: (1) the uvula-nodulus (lobules 9 and 10); (2) the flocculus, and (3) the anterior lobe vermis (lobules 1 and 2). Regional differences in ChAT-positive afferent terminations in the cerebellar cortex demonstrated by immunohistochemistry were confirmed by regional biochemical measurements of ChAT activity. Using ChAT immunohistochemistry in combination with HRP injections into the uvula-nodulus, we have studied the origin of the cholinergic projection. The caudal medial vestibular nucleus and to a lesser extent the nucleus prepositus hypglossus contain ChAT-positive neurons that were double labeled following HRP injections into the uvula-nodulus. We conclude that (1) there is a prominent cholinergic mossy fiber pathway to the vestibulocerebellum, (2) this pathway originates primarily in the caudal third of the medial vestibular nucleus, and (3) this cholinergic pathway likely mediates secondary vestibular information related to postural adjustment.

Ontogenesis of cerebellar afferents identified by cholecystokinin-like immunoreactivity

The present account provides a developmental timetable for the maturation of cholecystokinin (CCK)-positive fibers in the cerebellar cortex and cerebellar nuclei of the opossum. CCK-positive fibers are in the cerebellar peduncle by postnatal day (PD) 1, however they wait until PD 7 to penetrate the cerebellar anlage. Between PD 7 and PD 20 the fibers wait again in the medullary core of the cerebellum. After PD 20, there are 2 distinct patterns of CCK localization within the overlying cortical layers. The first pattern develops between PD 20–26 when CCK puncta are present in restricted foci within the Purkinje cell layer of the anterior lobe vermis. They distribute in 4 parasagittal bands, 2 on either side of the midline, that extend from the primary fissure rostrally into the anterior lobe of the cerebellum. By PD 33 two additional parasagittal bands are present in the posterior lobe vermis. The vast majority of these CCK puncta are transient in nature as all but a few disappear by PD 84. Those that remain progress through a series of developmental stages characteristics of climbing fiber ontogeny. These climbing fibers persist in lobules V, VII and VIII of the adult cerebellum. Further, there is a transient expression of CCK-immunoreactivity within inferior olivary neurons. These observations support the interpretation that the transient population of CCK-IR puncta are immature climbing fiber axons derived from the inferior olive. The second pattern of CCK localization is evident between PD 30–33, the time when granule cells first can be recognized in a histologically distinct internal granule cell layer (IGL). Between PD 30 and PD 68 there is a differential pattern of distribution of CCK-IR profiles within the lobules of the cerebellum. Initially, CCK-IR axons are only present in the anterior vermis where they are aligned in register with the bands of CCK puncta in the Purkinje cell layer. CCK-IR puncta are not present in the posterior lobe vermis or hemispheres until later stages of development. Further, a sagittal organization is not evident in either of these latter 2 areas. Initially, CCK-IR profiles in the IGL cannot be identified as mossy fibers based on their terminal morphology. When they first enter the IGL they appear as punctate elements. Over time they become increasingly more complex in shape and between PD 68–84 develop morphological characteristics of adult mossy fiber rosettes. The cerebellar nuclei can be distinguished histologically by PD 18, but CCK-IR fibers are not evident among these neurons until PD 36 which corresponds to about the time they can be visualized in the IGL. In addition, CCK-IR cell bodies first appear in the cerebellar nuclei between PD 26–30; these are present in the adult. The temporal expression of CCK within the developing IGL described in this account provides evidence for a differential lobular developments of mossy fibers. The transient expression of CCK-IR in the Purkinje cell layer suggests a role for these fibers in the sagittal organization of mossy fibers in the anterior lobe vermis.

Purkinje cell axon collateral distribution reflect the chemical compartmentation of the rat cerebellar cortex

Monoclonal antibody mabQ113 has been used to study the distribution of Prukinke cell axon collaterals in the rat cerebellar cortex. MabQ113 recognizes a polypeptide antigen, zebrin I, that is confined to a subset of Purkinje cells. Antigenic Purkinje cells are arranged in parasagittal compartments running throughout the cortex. No other cerebellar cells are immunoreactive. Immunoreactive axon collaterals are confined principally to the infraganglionic plexus with only a few extending into the molecular layer. Three probable target cells for the axon collaterals have been identified: Golgi cells, Lugaro cells, and other Purkinje cells. About 90% of immunoreactive axon collaterals in the anterior lobe are located beneath the mabQ113+ Purkinje cell compartment in which they originate but some do invade the neighboring mabQ113-territory. In the anterior lobe vermis, the distribution of invading mabQ113+ collaterals is not symmetrical, such that the probability of an invading collateral from the P2+ compartment is greater at the medial boundary into P1-than at the lateral into P2-. The distribution of immunoreactive collaterals is consistent with their playing a role in synchronizing the firing of Purkinje cells within the same compartment.

Chapter 1 Vestibular nuclei: afferent and efferent projections

Vestibular ganglion cells innervating the utricle project upon neurons in the ventral LVN; cells innervating the saccule project upon ventral LVN, group y and lateral IVN, while ganglion cells innervating the cristae ampullaris of the SD project mainly upon MVN and SVN. Cerebellar afferents to the VN arise ipsilaterally from the anterior lobe vermis (LVN), the flocculus (SVN, MVN and y ), the nodulus and uvula (MVN, IVN) and bilaterally from the fastigial nucleus (LVN, IVN). Commissural systems interconnect the MVN and peripheral SVN. The MVN, IVN and LVN receive modest projections from the dorsal regions of medullary and pontine RF. The SVN projects crossed and uncrossed fibres to TN and the OMC. The VST arises from the LVN and parts of other VN, provides collaterals to the LRN and projects preferentially upon cervical and lower lumbar segments by an elaborate collateral system. The MVN supplies the nuclei of the EOM and collaterals to cervical spinal segments. The IVN has diverse projections to the TN and the OMC, parts of the inferior olive, specific reticular nuclei, the cerebellum and the cervical spinal cord.

Studies on the central afferents to Deiters nucleus by the WGA-HRP method

The labyrinthine reflex is influenced by changes of head position. To elucidate the anatomical pathway involved in this reflex, the author studied the afferent route by the retrograde WGA-HRP method in cats. After the injection of HRP into either the dorsal or the ventral Deiters nucleus, labeled neurons were investigated in the spinal cord, cerebellum, contralateral vestibular nucleus complex and brain stem nucleus.1) When WGA-HRP was injected into the dorsal Deiters nucleus, labeled neurons in the spinal cord were found mainly extending from the cervical to the lumbosacral spinal cord. A number of labeled cells were located predominantly contralaterally in the cervical segments, while a small number of labeled cells were found ipsilaterally in the lumbosacral segments. In the case of the ventral Deiters nucleus, labeled neurons were found extending from the cervical to the upper thoracic cord. Localization of la-beled neurons in the spinal cord was limited mainly to Rexeds laminae VII, VIlI.2) When WGA-HRP was injected into the dorsal Deiters nucleus, Purkinje cells were labeled in the cerebellar cortex. Most of them were restricted to the anterior lobe vermis ipsilaterally. In the case of the ventral Deiters nucleus, labeled neurons were found in the fastigi nucleus. Most of them were localized in the rostral region contralaterally.3) When WGA-HRP was injected into the dorsal Deiters nucleus, no labeled neurons were found in the contralateral vestibular nucleus complex. In the case of the ventral Deiters nucleus, a few labeled neurons were found in the superior, medial, descending and ventral Deiters nucleus.4) When WGA-HRP was injected into the dorsal Deiters nucleus, labeled neurons in the brain stem nucleus were found in the lateral reticular nucleus, the inferior olive nucleus and the external cuneate nucleus, while a small number of labeled cells in the lateral reticular nucleus and the external cuneate nucleus were ipsilateral only. Labeled cells in the inferior olive nucleus were present contralaterally. In the case of the ventral Deiters nucleus, labeled neurons were found in the nucleus reticularis gigantocellularis, although a few labeled cells ware present contralaterally.These results suggest that Deiters nucleus may be functionally divided into two parts, dorsal and ventral. In addition, afferents to Deiters nucleus are considered to be closely related to the control of posture.

Double-labeling study of axonal branching within the lateral reticulocerebellar projection in the rat.

Collateral axonal branching to the cerebellum from the lateral reticular nucleus (LRN) was studied in the rat by using the fluorescent double-labeling technique. Following injection of Fast Blue (FB) into the cerebellar cortex, followed 3 days later by injection of Nuclear Yellow (NY) into a different region of the cortex, single- and double-labeled cells were found within the LRN. Most LRN-cerebellar projections were bilateral with ipsilateral preponderance, except for the projection to the paramedian lobule, which was completely ipsilateral. The dorsolateral area of the magnocellular division of the LRN contained cells whose axons branch to terminate in the rostral anterior lobe and the caudal part of the ipsilateral paramedian lobule (hindlimb areas of the cerebellar cortex), while the medial area of the LRN contained cells that supply, via collateral axonal branching, the caudal area of the contralateral anterior lobe and the rostral part of the ipsilateral paramedian lobule (forelimb areas of the cerebellum). Branched LRN-cerebellar axons projected to both hemispheres and to both sides of the caudal anterior lobe. No axonal branching was evident in the LRN-cerebellar projection to the rostral anterior lobe. The projection to the anterior and posterior lobe vermis also contained collateral axonal branching.

Input-output relations of lobules I and II of the cerebellar anterior lobe vermis in connexion with neck and vestibulospinal reflexes in the cat

In the anaesthetized cat, lobules I and II of the cerebellar anterior lobe vermis were examined to determine their role in the vestibulospinal and neck-vestibulospinal reflexes with respect to: (1) the somatotopic representation of afferent inputs from labyrinth, neck and tail; and (2) the inhibitory influence on vestibulospinal tract (VST) neurones receiving vestibular and neck afferent inputs. After electrical stimulation of the vestibular nerve and of neck afferents, almost identical responses via mossy fibres were evoked in the lobules, with the prominent response in lobules I and IIa of Larsell. Stimulation of the nerve supplying the dorsal region of the tail induced primarily the mossy fibre response, but also the climbing fibre response, in lobule II. The most responsive areas to tail and neck afferent stimulation did not overlap each other. In the lateral vestibular nucleus, 163 antidromically identified VST neurones were recorded extra- or intracellularly. On the basis of the response pattern to contralateral neck afferent stimulation, they were classified into 3 groups: (1) neurones with excitation ( n = 45); (2) neurones with inhibition ( n = 71); and (3) neurones with no modulation ( n = 47). Stimulation of lobules I–IIa inhibited the activities of 44 VST neurones. Out of them, 41 neurones belonged to the first group. They made up 91% of the group. Twenty-nine of these neurones, i.e. neurones receiving excitatory inputs from the neck and inhibitory inputs from the lobules, received additional excitatory input from the labyrinth. Although lobules I–IIa may be regarded as neck area in the anterior lobe vermis from the viewpoint of sensory input, they did not exert inhibitory influence only exceptionally on vestibulocollic neurones, but predominantly on VST neurones sending their axons to lower thoracic or more caudal segments in the spinal cord. It is suggested from these results that lobules I–IIa have a close relationship with the neck reflex and/or interaction of neck and vestibulospinal reflexes being concerned with the postural adjustment of a rather wide area of the body.

Input-output relations of lobules I and II of the cerebellar anterior lobe vermis in connexion with neck and vestibulospinal reflexes in the cat

In the anaesthetized cat, lobules I and II of the cerebellar anterior lobe vermis were examined to determine their role in the vestibulospinal and neck-vestibulospinal reflexes with respect to: (1) the somatotopic representation of afferent inputs from labyrinth, neck and tail; and (2) the inhibitory influence on vestibulospinal tract (VST) neurones receiving vestibular and neck afferent inputs. After electrical stimulation of the vestibular nerve and of neck afferents, almost identical responses via mossy fibres were evoked in the lobules, with the prominent response in lobules I and IIa of larsell. Stimulation of the nerve supplying the dorsal region of the tail induced primarily the mossy fibre response, but also the climbing fibre response, in lobule II. The most responsive areas to tail and neck afferent stimulation did not overlap each other. In the lateral vestibular nucleus, 163 antidromically identified VST neurones were recorded extraor intracellularly. On the basis of the response pattern to contralateral neck afferent stimulation, they were classified into 3 groups: (1) neurones with excitation ( n =45); (2) neurones with inhibition ( n =71); and (3) neurones with no modulation ( n =47). Stimulation of lobules I–IIa inhibited the activities of 44 VST neurones. Out of them, 41 neurones belonged to the first group. They made up 91% of the group. Twenty-nine of these neurones, i.e. neurones receiving excitatory inputs from the neck and inhibitory inputs from the lobules, received additional excitatory input from the labyrinth. Although lobules I–IIa may be regarded as neck area in the anterior lobe vermis from the viewpoint of sensory input, they did not exert inhibitory influence only exceptionally on vestibulocollic neurones, but predominantly on VST neurones sending their axons to lower thoracic or more caudal segments in the spinal cord. It is suggested from these results that lobules I–IIa have a close relationship with the neck reflex and/or interaction of neck and vestibulospinal reflexes being concerned with the postural adjustment of a rather wide area of the body.

Observations on the secondary vestibulocerebellar projections in the macaque monkey.

The distribution of retrogradely labeled cells in the nuclei of the vestibular nuclear complex following injections of horseradish peroxidase in various parts of the cerebellar cortex (except the nodulus and paraflocculus) has been mapped in the macacus rhesus monkey. In the main the findings correspond to those made in other mammalian species (cf. Table 1). The flocculus receives afferents bilaterally from the superior, medial and descending vestibular nucleus, group y, the interstitial nucleus of the vestibular nerve and also from the abducent nucleus. The projection to the posterior vermis (lobules VIII and IX), especially to lobule IX, is more abundant than that to lobules VI-VII. The projection to the anterior lobe vermis appears to be modest. Evidence for projections to the cerebellar hemispheres was not obtained. Whether the lateral vestibular nucleus projects to the cerebellum in the macaque is uncertain. The regular occurrence of weakly labeled cells among heavily labeled ones suggests that many of the cerebellar projecting cells may have axonal branches passing to other destinations. The findings lend support to the notion that there are precise topical relations within the entire secondary vestibulocerebellar projection. For example, in the medial nucleus the sites of origin of fibers to the flocculus and uvula are different. Surprisingly, many cells in group z were found to project to the uvula and - to a lesser extent - to lobule VIII. The group z may, therefore, not be a pure relay nucleus in a spinothalamic pathway, as generally assumed. The rather marked cerebellar projection of the abducent nucleus, especially to the flocculus, is of interest for the analysis of cerebellar control of eye movements in the macaque.

Selective retrograde labelling of the rat olivocerebellar climbing fiber system with d-[ 3h]aspartate

Selective retrograde labelling of the olivocerebellar climbing fiber system with d-[ 3H]aspartate has been observed in the rat, and the results have implications for the identification of a transmitter candidate as well as the neuroanatomical understanding of these cerebellar afferents. Microinjections of d-[ 3H]aspartate (50 nl, ca 10 -2 M) were made into various parts of cerebellar cortex. Survival times were 6,12 or 24 h. Pronounced diffusion of the tracer resulted in large injection sites. Within the zone of injection, glial elements were labelled over background. Most granule cells exposed to the tracer were unlabelled; the small numbers demonstrating labelling were believed to have been injured by the micropipette penetration. Beneath injection sites, large numbers of well-labelled nerve fibers appeared in the white matter and could be followed through the brainstem to the contralateral inferior olive, where labelled perikarya were found. After the inferior olivary neurons had been effectively destroyed with 3-acetylpyridine, evidence of cerebellar afferent labelling with d-[ 3H]aspartate was missing. Retrograde labelling of the olivocerebellar system was also observed after superfusion of the verrais with d-[ 3H] aspartate at concentrations in the range of K m for high affinity uptake (10 -5 or 10 -4 M, for 2 h). Mossy fiber or monoaminergic afferents to the cerebellum were never labelled with d-[ 3H]aspartate. The distribution of labelled cells in the olivary subnuclei after injections in different cerebellar areas was in line with the olivocerebellar organization previously described in the cat. Moreover, it was demonstrated that fibers from the different subnuclei follow different routes through the brainstem towards the cerebellum. Labelling of climbing fiber collaterals in uninjected parts of cerebellum indicated that some of the retrogradely migrating d-[ 3H]aspartate was directed in anterograde direction at axonal branching points. Collaterals were demonstrated in all deep cerebellar and Deiters' nuclei, and the results of intranuclear injections suggested that virtually every olivary neuron sends collaterals to these nuclei. Intracortical collaterals were organized in sagittal zones. Midline injections into the anterior lobe and VI lobule labelled collaterals in several zones of the posterior lobe spinal area and uninjected parts of the anterior lobe vermis. Hemispheral injection into copula pyramidis labelled collaterals in two prominent bundles in the anterior lobe. Injection into lobulus paramedianus and crus II gave massive collateral labelling in lobulus simplex, crus I, and laterally in lobuli IV–V, while fewer fibers ran to paraflocculus. Injection into lobulus simplex labelled collaterals in two or three zones of crus II and lobulus paramedianus. Injection into paraflocculus labelled collaterals in crus I, crus II and lobulus paramedianus. These results suggest that all olivocerebellar neurons share a selective affinity for d-[ 3H]aspartate, which is in line with proposals that aspartate may be their transmitter. Further, the study demonstrated the organization of the olivocerebellar pathway through the brainstem, and the complex pattern of climbing fiber collateralization to deep cerebellar nuclei and different regions of cerebellar cortex.

Regression of cerebellar syndrome with long-term administration of 5-HTP or the combination 5-HTP-benserazide

A quantitative evaluation of cerebellar ataxia, with an ataxia score (total, static, kinetic) and the measurement of objective values relating to the major symptoms, was used in 21 patients with hereditary ataxias treated for 12 months with high doses (16 mg/kg/day) of d-l-5-HTP, l-5-HTP or the combination d-l-5-HTP (16 mg/kg/day)--benserazide (6 mg/kg/day). The data obtained from regular examination were processed by computer. The ataxia showed a significant regression at the 12th month, mainly in the static forms and speed of speech. l-5-HTP appeared to be more effective than d-l-5-HTP. Regression of the cerebellar ataxia was also observed in non-degenerative conditions such as multiple sclerosis and surgical lesion of the anterior lobe vermis, showing that 5-HTP was active on the cerebellar syndrome in general. The regression of the cerebellar ataxia was very slow in inherited diseases and continued for 2 or 4 months after the treatment stopped. A serotoninergic cerebellar control of movement is discussed.

Afferent and efferent connections of the medial, inferior and lateral vestibular nuclei in the cat and monkey

Attempts were made to determine the afferent and efferent connections of the medial (MVN), inferior (IVN) and lateral (LVN) vestibular nuclei (VN) in the cat and monkey using retrograde and anterograde axoplasmic transport technics. Injections of HRP and [3H]amino acids were made selectively into MVN, IVN and LVN and into: (1) MVN and IVN, (2) LVN and IVN and (3) all 4 VN. Contralateral afferents to MVN arise from (1) the nuclei prepositus (NPP) and intercalatus (NIC), (2) all parts of MVN and cell group 'y' and (3) parts of the superior vestibular nucleus (SVN), IVN and the fastigial nucleus (FN). Ipsilateral projections to MVN arise from: (1) a central band of the flocculus and the nodulus and uvula, (2) the interstitial nucleus of Cajal (INC), and (3) visceral nuclei of the oculomotor nuclear complex (OMC). Efferent projections of MVN are to: (1) the ipsilateral supraspinal nucleus (SSN), and (2) the contralateral central cervical nucleus (CCN), MVN, SVN, cell group 'y', the rostroventral region of LVN, the trochlear nucleus (TN) and the INC. Projections to the abducens nuclei (AN) and the OMC are bilateral. Some ascending fibers in the cat cross within the OMC. In the monkey fibers from MVN end in a central band of the ipsilateral flocculus. Afferents to IVN arise ipsilaterally from SVN, the nodulus, the uvula and the anterior lobe vermis. Contralateral afferents arise from: (1) parts of CCN, MVN, SVN, IVN and cell group 'y' and (2) the central third of the FN. IVN receives bilateral projections from the perihypoglossal nuclei (PH) and the visceral nuclei of the OMC. Efferents from IVN project: (1) ipsilaterally to nucleus beta of the inferior olive, (2) contralaterally to parts of MVN, SVN and cell group 'y' and (3) bilaterally to the paramedian reticular nuclei. No commissural fibers interconnect cell groups 'f' and 'x'. Ascending fibers from IVN terminate contralaterally in the TN and the OMC. In the monkey fibers from IVN terminate in the ipsilateral nodulus, uvula and anterior lobe vermis; no fibers project to FN in either the cat or the monkey. Afferents to the LVN arise primarily from the ipsilateral anterior lobe vermis and bilaterally from rostral parts of the FN. No commissural fibers interconnect the LVN. Projections of the LVN are primarily to spinal cord via the vestibulospinal tract (VST); collaterals of the VST terminate in the lateral reticular nucleus (LRN). Ascending uncrossed projections from LVN in the cat terminate in the medial rectus subdivision of the OMC.(ABSTRACT TRUNCATED AT 400 WORDS)

A horseradish peroxidase study of the projections from the lateral reticular nucleus to the cerebellum in the rat.

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 orgins 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.