The olivocerebellar projection to the uvula in the mouse

Inferior olive and oculomotor system

Three subnuclei within the inferior olive are implicated in the control of eye movement; the dorsal cap (DC), the beta-nucleus and the dorsomedial cell column (DMCC). Each of these subnuclei can be further divided into clusters of cells that encode specific parameters of optokinetic and vestibular stimulation. DC neurons respond to optokinetic stimulation in one of three planes, corresponding to the anatomical planes of the semicircular canals. Neurons in the beta-nucleus and DMCC respond to vestibular stimulation in the planes of the vertical semicircular canals and otoliths. Each these olivary nuclei receives excitatory and inhibitory signals from pre-olivary structures. The DC receives excitatory signals from the ipsilateral nucleus of the optic tract (NOT) and inhibitory signals from the contralateral nucleus prepositus hypoglossi (NPH). The beta-nucleus and DMCC receive inhibitory signals from the ipsilateral nucleus parasolitarius (Psol) and excitatory signals from the contralateral dorsal Y group. Consequently, the olivary projection to the cerebellum, although totally crossed, still represents bilateral sensory stimulation. Inputs to the inferior olive from the NOT, NPH, Psol or Y-group discharge at frequencies of 10-100 imp/s. CFRs discharge at 1-5 imp/s; a frequency reduction of an order of magnitude. Inferior olivary projections to the contralateral cerebellum are sagittally arrayed onto multiple cerebellar folia. These arrays establish coordinate systems in the flocculus and nodulus, representing head-body movement. These climbing fiber-defined spatial coordinate systems align Purkinje cell discharge onto subjacent cerebellar and vestibular nuclei. In the oculomotor system, olivo-cerebellar circuitry enhances and modifies eye movements based on movement of the head-body in space.

Horizontal rectus muscle tenotomy in children with infantile nystagmus syndrome: a pilot study

PURPOSE

We wished to determine the effectiveness of horizontal rectus tenotomy in changing the nystagmus of children with infantile nystagmus syndrome.

DESIGN

This was a prospective, noncomparative, interventional case series in five children with varied sensory and oculographic subtypes of congenital nystagmus (including asymmetric (a)periodic alternating nystagmus) and no nystagmus treatment options. Simple tenotomy of all four horizontal recti with reattachment at the original insertion was accomplished. Search-coil and infrared eye movement recordings and clinical examinations were performed before and 1, 6, 26, and 52 weeks after surgery. Outcome measures included masked pre- and postoperative expanded nystagmus acuity function (NAFX), foveation time obtained directly from ocular motility recordings, and masked measures of visual acuity.

RESULTS

At 1 year after tenotomy and under binocular conditions, two of the three patients for whom the NAFX could be measured had persistent, significant postoperative increases in the NAFX of their fixating eye. Average foveation times increased in these patients' fixating eyes. Measured binocular visual acuity increased in four patients; the remaining patient had retinal dystrophy. There were no adverse events due to surgery.

CONCLUSIONS

In the two children who could fixate the targets for several seconds and for whom we could obtain accurate measurements of their infantile nystagmus, tenotomy resulted in significant improvements in nystagmus foveation measures. In those patients plus two others (four of five), measured visual function improved.

The ventral uvula of the mouse cerebellum: a neural target of ethanol and vestibular stimuli

The present study demonstrates that mice exposed to vertical translation stimulation exhibit a distinct parasagittal pattern of Fos-immunoreactive (Fos-IR) granule cells in the ventral uvula of the cerebellum. This pattern is identical to one produced by acute ethanol treatment. In contrast, yaw stimulation produces an entirely different pattern in this same region of the cerebellum. Similar results are obtained in the light or in total darkness. These results suggest an anatomical and functional organization within the granule cells of the ventral uvula that may be a common neural substrate for some effects of ethanol and particular vestibular stimuli.

Horizontal rectus tenotomy in patients with congenital nystagmus

OBJECTIVE

We wished to determine the effectiveness of horizontal rectus tenotomy in changing the nystagmus of patients with congenital nystagmus and, secondarily, how their visual function changed.

DESIGN

This was a prospective, noncomparative, interventional case series.

PARTICIPANTS

Ten adult patients with varied associated sensory defects and oculographic subtypes of congenital nystagmus (including asymmetric periodic or aperiodic alternating nystagmus) and no nystagmus treatment options.

METHODS

By using standard surgical techniques, simple tenotomy of all four horizontal recti with reattachment at the original insertion was accomplished. Search-coil eye movement recordings and clinical examinations were performed before and 1, 6, 24, and 52 weeks after surgery.

MAIN OUTCOME MEASURES

The primary outcome measure was the expanded nystagmus acuity function, obtained in "masked" fashion directly from ocular motility recordings. Secondary outcomes included breadth of null zones, preoperative and postoperative masked measures of visual acuity (Early Treatment Diabetic Retinopathy Study [ETDRS] chart), and the National Eye Institute Visual Function Questionnaire (NEI-VFQ-25).

RESULTS

At 1 year after tenotomy and under binocular conditions, 9 of 10 patients had persistent, significant postoperative increases in the expanded nystagmus acuity function of their fixing (preferred) eye; 1 remained high, and 1 was not tested under the same conditions. Average foveation times increased in all 9 fixing (preferred) eyes. Binocular visual acuity measured with the ETDRS chart increased in 5 patients and was unaffected in five, whereas the NEI-VFQ-25 showed an improvement in vision-specific mental health in 9 patients. There were no adverse events. Tenotomy also radically changed the periodicity of one patient's asymmetric periodic or aperiodic alternating nystagmus.

CONCLUSIONS

In 9 of 10 adult patients with clinical and oculographic variations in their congenital nystagmus, tenotomy resulted in significant improvements in a nystagmus measure and subjective visual functions.

Acute ethanol administration produces specific patterns of localization of Fos-immunoreactivity in the cerebellum and inferior olive of two inbred strains of mice

Genes play an important role in behavioral responses to ethanol. We examined the response of neurons within the inferior olivary complex (IO) and cerebellum of C57Bl6/J and C3H/HeJ mice to acute ethanol, using immunodetection of Fos (Fos-IR) protein as a marker of neuronal activation. The results demonstrate specific but different patterns of Fos-IR within the IO and cerebellum, especially lobule IX, in each strain. The Fos-IR banding pattern seen in the granule cells of lobule IX is aligned with a previously described banding pattern of Purkinje cells that constitutively expressed heat-shock protein-25 (HSP-25).

Vestibular signals in the parasolitary nucleus

Vestibular primary afferents project to secondary vestibular neurons located in the vestibular complex. Vestibular primary afferents also project to the uvula-nodulus of the cerebellum where they terminate on granule cells. In this report we describe the physiological properties of neurons in a "new" vestibular nucleus, the parasolitary nucleus (Psol). This nucleus consists of 2,300 GABAergic neurons that project onto the ipsilateral inferior olive (beta-nucleus and dorsomedial cell column) as well as the nucleus reticularis gigantocellularis. These olivary neurons are the exclusive source of vestibularly modulated climbing fiber inputs to the cerebellum. We recorded the activity of Psol neurons during natural vestibular stimulation in anesthetized rabbits. The rabbits were placed in a three-axis rate table at the center of a large sphere, permitting vestibular and optokinetic stimulation. We recorded from 74 neurons in the Psol and from 23 neurons in the regions bordering Psol. The activity of 72/74 Psol neurons and 4/23 non-Psol neurons was modulated by vestibular stimulation in either the pitch or roll planes but not the horizontal plane. Psol neurons responded in phase with ipsilateral side-down head position or velocity during sinusoidal stimulation. Approximately 80% of the recorded Psol neurons responded to static roll-tilt. The optimal response planes of evoked vestibular responses were inferred from measurement of null planes. Optimal response planes usually were aligned with the anatomical orientation of one of the two ipsilateral vertical semicircular canals. The frequency dependence of null plane measurements indicated a convergence of vestibular information from otoliths and semicircular canals. None of the recorded neurons evinced optokinetic sensitivity. These results are consistent with the view that Psol neurons provide the vestibular signals to the inferior olive that eventually reached the cerebellum in the form of modulated climbing fiber discharges. These signals provide information about spatial orientation about the longitudinal axis.

Transneuronal pathways to the vestibulocerebellum

The alpha-herpes virus (pseudorabies, PRV) was used to observe central nervous system (CNS) pathways associated with the vestibulocerebellar system. Retrograde transneuronal migration of alpha-herpes virions from specific lobules of the gerbil and rat vestibulo-cerebellar cortex was detected immunohistochemically. Using a time series analysis, progression of infection along polyneuronal cerebellar afferent pathways was examined. Pressure injections of > 20 nanoliters of a 10(8) plaque forming units (pfu) per ml solution of virus were sufficient to initiate an infectious locus which resulted in labeled neurons in the inferior olivary subnuclei, vestibular nuclei, and their afferent cell groups in a progressive temporal fashion and in growing complexity with increasing incubation time. We show that climbing fibers and some other cerebellar afferent fibers transported the virus retrogradely from the cerebellum within 24 hours. One to three days after cerebellar infection discrete cell groups were labeled and appropriate laterality within crossed projections was preserved. Subsequent nuclei labeled with PRV after infection of the flocculus/paraflocculus, or nodulus/uvula, included the following: vestibular (e.g., z) and inferior olivary nuclei (e.g., dorsal cap), accessory oculomotor (e.g., Darkschewitsch n.) and accessory optic related nuclei, (e.g., the nucleus of the optic tract, and the medial terminal nucleus); noradrenergic, raphe, and reticular cell groups (e.g., locus coeruleus, dorsal raphe, raphe pontis, and the lateral reticular tract); other vestibulocerebellum sites, the periaqueductal gray, substantia nigra, hippocampus, thalamus and hypothalamus, amygdala, septal nuclei, and the frontal, cingulate, entorhinal, perirhinal, and insular cortices. However, there were differences in the resulting labeling between infection in either region. Double-labeling experiments revealed that vestibular efferent neurons are located adjacent to, but are not included among, flocculus-projecting supragenual neurons. PRV transport from the vestibular labyrinth and cervical muscles also resulted in CNS infections. Virus propagation in situ provides specific connectivity information based on the functional transport across synapses. The findings support and extend anatomical data regarding vestibulo-olivo-cerebellar pathways.

Topography of Purkinje cell compartments and mossy fiber terminal fields in lobules II and III of the rat cerebellar cortex: spinocerebellar and cuneocerebellar projections

The cerebellar cortex is histologically uniform by conventional staining techniques, but contains an elaborate topography. In particular, on the efferent side the cerebellar cortex can be subdivided into multiple parasagittal compartments based upon the selective expression by Purkinje cell subsets of various molecules, for example the polypeptide antigens zebrin I and II, and on the afferent side many mossy fibers terminate as parasagittal bands of terminals. The relationships between mossy fiber terminal fields and Purkinje cell compartments are important for a full understanding of cerebellar structure and function. In this study the locations of spino- and cuneocerebellar mossy fiber terminal fields in lobules II and III of the rat cerebellum are compared to the compartmentation of the Purkinje cells as revealed by using zebrin II immunocytochemistry. Wheat germ agglutinin-horseradish peroxidase was injected at three different levels in the spinal cord and in the external cuneate nucleus, and the terminal field distributions in lobules II and III of the cerebellar cortex were compared with the Purkinje cell compartmentation. In the anterior lobe, zebrin II immunocytochemistry reveals three prominent, narrow immunoreactive bands of Purkinje cells, P1+ at the midline and P2+ laterally at each side. These are separated and flanked by wide zebrin- compartments (P1- and P2-). There are also less strongly stained P3+ and P4+ bands more laterally. The spinocerebellar terminals in the granular layer are distributed as parasagittally oriented bands. Projections from the lumbar region of the spinal cord terminate in five bands, one at the midline (L1), a second with its medial border midway across P1- and its lateral border at the P2+/P2- interface (L2), and a third extending laterally from midway across P2-. The lateral edge of L3 may align with the P3+/P3- border. The terminal fields labeled by a tracer injection into the thoracic region give a very similar distribution (T1, T2 and T3). The only systematic difference is in T2, which statistical analysis suggests may be broader than L2. In contrast, anterograde tracer injections into the cervical region label synaptic glomeruli scattered throughout the lobule with much weaker or no evidence of banding. The terminal fields of the cuneocerebellar projection have a complementary distribution to those of thoracic and lumbar spinocerebellar terminals. There are two lateral bands, Cu2 and Cu3. Cu2 lies within the Purkinje cell P1-compartment, abutting L1/T1 medially and L2/T2 laterally. Cu3 lies between L2 and L3 within the P2- Purkinje cell compartment. The medial edge of Cu3 is tightly aligned with the P2+/P2- border.(ABSTRACT TRUNCATED AT 400 WORDS)

External cuneocerebellar projection and Purkinje cell zebrin II bands: a direct comparison of parasagittal banding in the mouse cerebellum

The parasagittal parcellation of the mammalian cerebellar cortex has been revealed using anatomical, electrophysiological, histological and immunological techniques. Correlation studies have been carried out to determine whether a common organizational plan encompassing the various afferent, efferent and intrinsic maps may exist in the mammalian cerebellum. Many of these studies utilized the parasagittal Purkinje cell antigenic banding pattern as revealed by the monoclonal antibody against zebrin antigens as a standard reference. In this study, the pattern of labelled mossy fiber terminals originating from the external cuneate nucleus was determined and compared with the Purkinje cell antigenic zebrin bands in the same sections. External cuneocerebellar fibers in the mouse were observed to project in well-delineated parasagittal terminal distribution zones, primarily to the ipsilateral vermal cerebellar cortex. However, there was a very minor, but consistent contralateral component. The external cuneocerebellar fiber termination pattern in the mouse differed from that seen in other rodents such as the rat. Comparison of the external cuneucerebellar terminal zones in sections immunohistochemically stained for the zebrin II antigen revealed that the boundaries of the terminal fields of the external cuneocerebellar projection do not always align with those of the zebrin II antigenic bands. These results strongly suggest that mossy fibers have a complicated relationship to zebrin defined compartments. Therefore, the designation 'functional unit' of the cerebellum or 'cerebellar module' remains uncertain at this time.

The olivocerebellar projection in normal (+/+), heterozygous weaver (wv/+), and homozygous weaver (wv/wv) mutant mice: comparison of terminal pattern and topographic organization

Olivocerebellar organization and topography were analyzed in adult normal (+/+), heterozygous weaver (wv/+), and homozygous weaver (wv/wv) mutant mice. The two genotypes (wv/+ and wv/wv) of the weaver mutant present a gradation of abnormal cerebellar morphology. Purkinje cell (PC) ectopia ranges from mild (wv/+) to moderate (wv/wv), and regional PC loss is also graded in the two types. To determine olivocerebellar organization and topography, tritiated amino acids were placed into different regions of the inferior olivary complex (IO) in normal, heterozygous, and homozygous weaver mice. Despite some PC loss and ectopia, olivocerebellar fiber (OCF) terminals in both homozygous and heterozygous weaver mice have an orthogonal distribution and topography similar to that seen in normal mice. Differences in OCF termination, such as an increased density of OCF terminal label in the lower portion of the molecular layer, the PC, and granule cell layers, are seen in homozygous weaver mice. In some heterozygous weaver and normal cases, multiple injections labeling most IO cells on one side of the IO resulted in continuous OCF terminal labeling in many regions of the contralateral cerebellar cortex, suggesting that all PCs receive OCF input. Retrograde analysis involving injections of horseradish peroxidase conjugated to wheat germ agglutinin into different mediolateral cerebellar regions in homozygous weaver mice further demonstrates a generally normal olivocerebellar topography.

Evidence of early topographic organization in the embryonic olivocerebellar projection: a model system for the study of pattern formation processes in the central nervous system

Many projection systems within the peripheral and central nervous system are topographically organized, and it has become increasingly clear that interactions which occur during development determine the projection patterns these systems exhibit in the adult. The olivocerebellar system was chosen as a model system for this study of afferent pattern formation because it has several characteristics which lend themselves to a study of this type. Applications of horseradish peroxidase were made to both the cerebellar primordium and to the inferior olive of embryonic and neonatal mice using an in vitro perfusion system to support the tissue during the transport period. Fibers labeled after restricted olivary applications are limited to particular mediolateral regions of the cerebellum. Similarly, olivary cells retrogradely labeled after discrete cerebellar applications are restricted to particular olivary subdivisions. The results indicate that the olivocerebellar projection displays elements of topographic organization as early as E15 and that the pattern displayed is roughly comparable to that of the adult mammal. The observed trajectories of olivocerebellar fibers and their concomitant association with both Purkinje and cerebellar nuclear cells during embryonic development suggests a role for either or both cell types in the pattern formation process.

Olivary morphology and olivocerebellar topography in adult lurcher mutant mice

In adult lurcher mice, in which virtually all cerebellar Purkinje cells have degenerated as a direct consequence of mutant gene action, the inferior olivary complex suffers a severe retrograde transneuronal atrophy. Our analysis indicates a 63% cell loss in the lurcher inferior olive, homogeneously distributed between the medial and dorsal accessory, and principal olivary subdivisions. Olivary neurons are reduced in cross-sectional area by 30% in lurcher mice, compared to normal controls. All olivary subdivisions morphologically identifiable in normal mice are also found in the lurcher inferior olive. Analysis of olivocerebellar topography by retrograde transport of lectin-conjugated horseradish peroxidase and fluorogold, in both single and double labeling paradigms, reveals no abnormalities in the general organization of this highly ordered projection. This stability may be based on the initial establishment of the topographic pattern in late embryogenesis or early postnatal periods, prior to the onset of lurcher Purkinje cell degeneration, or, alternatively, the lurcher gene may not alter critical afferent and target characteristics at stages when the topographic relationship is being established. Once established, the olivocerebellar projection is apparently not dependent on the Purkinje cell for long-term maintenance of its general topographic organization.

Columnar organisation of the inferior olive projection to the posterior lobe of the rat cerebellum

The organisation of the olivocerebellar projection to lobules VI, VIII, and IX of the posterior lobe of the rat cerebellum was investigated in detail by using the retrograde tracer wheat germ agglutinin-horseradish peroxidase. Small, well-defined rostro-caudally orientated columns of olive cells were found to project to different parasagittal areas in the posterior lobe. A column of olive cells about 2,000 microns in rostro-caudal length in subnucleus "c" and nucleus beta of the caudal medial accessory olive (MAO) provides climbing fibre input to the most medial part of lobules VI and IX, but this projection is displaced laterally in lobule VIII by a projection from a column of cells about 600 microns in rostro-caudal length in lateral caudal MAO (subnucleus "a"). It is possible that each of these columns of olivary neurones may be further subdivided in the rostro-caudal axis so that different sections project to different medio-lateral parts of the cortex. A fine-grain 'sublobular' localisation may also exist: the projection to midline lobule VIc arises at caudal levels of the olive from a band of cells in the transition region between subnucleus "c" and nucleus beta, whilst by comparison the projection from caudal levels of the olive to lobules VIa and VIb arises from cells located more ventrally in nucleus beta. Evidence is also presented to confirm that the posterior lobe vermis in the rat extends further laterally than in other mammals and that part of it receives a projection from a column of olive cells, 1,000 microns in rostro-caudal length, in a newly defined region of caudal MAO, termed subnucleus "b1."

Expression of compartmentation antigen zebrin I in cerebellar transplants

The mammalian cerebellum is divided into multiple parasagittal compartments as defined by the organization of afferent and efferent projections and by the pattern of expression of several biochemical markers. One such marker is the antigen zebrin I, a 120 kD polypeptide of unknown function that is expressed differentially by a subset of Purkinje cells. Zebrin I+ Purkinje cells are grouped into an array of 14 parasagittal bands interposed by zebrin I- compartments. This Purkinje cell compartmentation corresponds to compartments in the olivocerebellar projection. The afferent axon compartments are present prior to the expression of the mature zebrin I phenotype, thus raising the possibility that differential afferent input regulates the zebrin I phenotype of the target of that input. Lesion studies in the neonate preclude a role for afferent inputs in the regulation of zebrin I expression postnatally, but a prenatal role in commitment still remains open. To explore this possibility, cerebellar anlagen were dissected from embryos at embryonic days 12-15, that is, prior to any contact with afferents, and transplanted ectopically into adult hosts. In the first series of experiments, the grafts were placed into the anterior chamber of the eye, and in the second series, into cavities prepared in the neocortex. Grafts were allowed to mature and then were immunoperoxidase or immunofluorescence stained for zebrin I immunoreactivity. Zebrin I was expressed by grafted Purkinje cells in cortico and in oculo. Double-labelling experiments confirmed that both the zebrin I+ and the zebrin I- phenotypes were present. The zebrin I immunoreactivity revealed that the zebrin I+ Purkinje cells resemble those in situ with an extensive dendritic arborization that extends through the molecular layer perpendicular to the long axes of the folia. In conclusion, the present data suggest that afferent input does not play a role in the determination of the zebrin I phenotype of Purkinje cells.

Zebrin II: a polypeptide antigen expressed selectively by Purkinje cells reveals compartments in rat and fish cerebellum

Monoclonal antibody mab-zebrin II was generated against a crude homogenate of cerebellum and electrosensory lateral line lobe from the weakly electric fish Apteronotus leptorhynchus. On Western blots of fish cerebellar proteins, mab-zebrin II recognizes a single polypeptide antigen of apparent molecular weight 36 kD. Immunocytochemistry of apteronotid brains reveals that zebrin II immunoreactivity is confined exclusively to Purkinje cells in the corpus cerebelli, lateral valvula cerebelli, and the eminentia granularis anterior. Other Purkinje cells, in the medial valvula cerebelli and eminentia granularis posterior, are not zebrin II immunoreactive. Immunoreactive Purkinje cells are stained completely, including dendrites, axons, and somata. The antigen seems to be absent only from the nucleus. A similar distribution is seen in catfish, goldfish, and a mormyrid fish. Zebrin II immunoreactivity is also found in the rat cerebellum. Western blotting of rat cerebellar proteins reveals a single immunoreactive polypeptide, with apparent molecular weight 36 kD, as in the fish. Also as in the fish, staining in the adult rat cerebellum is confined to a subset of Purkinje cells. Peroxidase reaction product is deposited throughout the immunoreactive Purkinje cells with the exception of the nucleus. No other cells in the cerebellum express zebrin II. At higher antibody concentrations, a weak glial cross reactivity is seen in most other brain regions: we believe that this is probably nonspecific. Zebrin II+ Purkinje cells are clustered together to form roughly parasagittal bands interposed by similar nonimmunoreactive clusters. In all there are 7 zebrin II+ and 7 zebrin II- compartments in each hemicerebellum. One immunoreactive band is adjacent to the midline; two others are disposed laterally to each side in the vermis; there is a paravermal band; and finally three more bands are identified in each hemisphere. Both in number and position, these compartments correspond precisely to the bands revealed by using another antibody, mabQ113 (anti-zebrin I). In both fish and rat the compartmentation revealed by zebrin II immunocytochemistry is related to the organization of cerebellar afferent and efferent projections and may provide clues as to the fundamental architecture of the vertebrate cerebellum.

Organization and postnatal development of zebrin II antigenic compartmentation in the cerebellar vermis of the grey opossum, Monodelphis domestica

The mammalian cerebellar cortex consists of a number of parasagittal Purkinje cell compartments that can be demonstrated cytochemically. The afferent inputs to the cerebellum are also compartmentalized, and a complex but reproducible relationship exists between the afferents and the intrinsic maps. Developmental studies in the rat have shown that many of the main features of compartmentation are already established at birth, and are therefore not easily manipulated experimentally. The compartmentation antigen zebrin II is expressed selectively by Purkinje cell subsets in a range of species, including fish and primates. In this study, zebrin II immunoreactivity has been studied in the grey opossum, Monodelphis domestica, in order to develop a marsupial model of compartment formation in which the early developmental events are more readily accessible. A monoclonal antibody to zebrin II from the weakly electric fish Apteronotus recognizes a 36 kD polypeptide in homogenates of Monodelphis cerebellum that appears to be identical to the antigen in the rat. Immunocytochemistry reveals that zebrin II in adult Monodelphis is confined exclusively to the cerebellum, where it is expressed by a subset of Purkinje cells. All regions of the cell, except the nucleus, are stained. The zebrin II+ Purkinje cells are arranged in a set of parasagittal compartments interposed by similar zebrin II- compartments. In each hemicerebellum there is one zebrin II+ band abutting the midline (P1+), and two others laterally in the vermis (P2+, P3+). A fourth zebrin II+ compartment straddles the paravermian region (P4+). Three other compartments have been identified in the hemisphere (P5+, P6+, P7+). This arrangement is very similar to that found in the rat. During postnatal development, zebrin II is first expressed between P14 and P21 in Purkinje cells of the posterior lobe vermis, and spreads throughout the cerebellar cortex by P28. As in rat, there is a stage at which all Purkinje cells are zebrin II+, including those destined to be zebrin II- in the adult. The mature pattern of expression emerges after P35 as immunoreactivity gradually disappears from the cells destined to become zebrin II-. The adult appearance is attained only after P56. The developmental timetable is therefore similar to that in rat, but is rather more protracted. Monodelphis should prove to be a valuable experimental model in which to study the early events leading to the formation of cerebellar compartments.

Parasagittal organization of the rat cerebellar cortex: direct comparison of Purkinje cell compartments and the organization of the spinocerebellar projection

Retrograde and anterograde transport of tracers, electrophysiological recording, somatotopic mapping, and histochemical and immunological techniques have all revealed a parasagittal parcellation of the cerebellar cortex, including its efferent and many of its afferent connections. In order to establish whether the different compartments share a common organizational plan, a systematic comparative analysis of the patterns of parasagittal zonation in the cerebellar cortex of the rat has been undertaken, by using the parasagittal compartmentation of zebrin I+ and zebrin I- Purkinje cells as revealed by monoclonal antibody Q113 as a reference frame. The distribution of mossy fiber terminals originating from the lower thoracic-higher lumbar spinal cord was compared to the distribution of zebrin I bands. Three-dimensional reconstructions from alternate frontal sections processed either for the anterograde transport of tracer or for zebrin I immunoreactivity reveal that the limits of the spinocerebellar terminal fields in the granular layer correlate well with the boundaries of some, but not all, zebrin I compartments in the molecular layer above. This leads to a subdivision of the zebrin I compartments into spinal receiving and spinal nonreceiving portions. In lobules II and VIII, the spinocerebellar terminal fields assume different positions relative to the zebrin I compartments in the ventral compared to the dorsal faces. Thus, each longitudinal compartment may be further divided transversely into subzones, each receiving a specific combination of mossy fiber afferents. The further subdivision of zebrin I compartments by mossy fiber terminal fields increases the resolution of the topography to such a point that anatomical compartment widths become compatible with the width of the microzones and the patches identified by electrophysiological methods.

Zonal organization of climbing fiber projections to the uvula in the cat

Climbing fiber projections from the inferior olive to the uvula of the cerebellum were studied in the cat by using retrograde axonal transport of horseradish peroxidase. Following large and small injections into various parts of the uvula, the distribution of labeled cells in the inferior olive was investigated. The findings indicate six longitudinal zones extending throughout the dorsal and ventral uvula: the caudal part of the nucleus beta projects to a most medially located zone (caudal beta zone) with a width of about 0.4 mm; the rostral part of the nucleus beta projects to a zone located at about 0.6 mm from the midline (rostral beta zone); the caudal part of the medial accessory olive (MAO) projects to a zone (caudal MAO zone) located lateral to the rostral beta zone; the dorsomedial cell column projects to a zone (dorsomedial cell column zone) located in the intermediate part of the uvula at about 1.2 mm from the lateral edge of the uvula; the ventral lamella of the principal olive (PO) projects to a zone (ventral lamella of PO zone) about 0.7 mm from the lateral edge of the uvula; finally, the rostral part of the MAO projects to the most lateral zone (rostral MAO zone). These conclusions are in general agreement with those of earlier studies and also provide a more detailed zonal configuration of climbing fiber projections to the uvula.

Sagittal organization of the olivocerebellonuclear pathway in the rat. I. Connections with the nucleus fastigii and the nucleus vestibularis lateralis

The organization of the afferent and efferent connections of the sagittal Zones A and B of the cerebellar cortex of the rat have been studied using wheat-germ agglutinin conjugated to horseradish peroxidase as a tracer. A single injection of this tracer into the cerebellar cortex allowed us to study, simultaneously, the crossed olivocortical connections (revealed by the retrograde transport) and the direct corticonuclear connections (revealed by the anterograde transport). The results demonstrate that the olivocerebellonuclear pathway is organized in a longitudinal direction so that for a given small injection of the tracer in one lobule of the cortex, a long sagittal band of the retrograde-labelled cells is obtained in the inferior olive, and a long sagittal band of the labelled terminals is obtained in the cerebellar nuclei. Zone A and Zone B have been arbitrarily defined as the cortical regions projecting, respectively, to the nucleus fastigii (NF) and the nucleus vestibularis lateralis (NVL). Zone A of the rat runs parasagitally from lobules I to IX as described in the cat, but in the posterior lobe it extends much more laterally than in the other mammals to include the lobulus paramedianus and crus I regions. The projections of Zone A to the NF recognize a mediolateral as well as a dorsoventral organization. Zone A receives climbing fibres exclusively from the caudal half of the medial accessory olive (MAO) with a further topographical organization in 4 distinct connections. Zone B of the rat is a narrow strip of the cortex lying adjacent to Zone A and extending from lobule I to VI. It receives climbing fibres from the caudolateral half of the dorsal accessory olive (DAO) and projects to the ipsilateral NVL with no other detectable organization. The majority of the labelled terminals end in the dorsal aspect of the NVL, but a non-negligible quantity also end in the ventral aspect.

Topographical distribution of muscarinic cholinergic receptors in the cerebellar cortex of the mouse, rat, guinea pig, and rabbit: a species comparison

Light microscopic autoradiography of [3H]quinuclidinyl benzilate (QNB) binding sites was used to study the distribution of muscarinic acetylcholine receptors in the mouse, rat, guinea pig, and rabbit cerebellar cortex. In the mouse, the laminar distribution of grain density was similar throughout the cortex, with slightly higher levels over lobules IX and X. The highest [3H]QNB labeling was present over the granule cell layer, and low levels were observed over the molecular layer. In the rat, the general distribution was similar to that of the mouse in that the granule cell layer was most densely labeled and the highest concentration of [3H]QNB binding sites was present in lobules IX and X of the archicerebellum. In these lobules, however, the laminar distribution of grain density was reversed so that the molecular layer was more densely labeled than the granule cell layer. In addition, several discrete columns of elevated grain density traversed the granule cell layer in caudal regions of lobule IX. The distribution of [3H]QNB binding sites in the guinea pig cerebellum was similar to that of the rat in that the molecular layer of lobules IX and X was again more intensely labeled than other cerebellar regions. In the remaining lobules, grain density was equal over the granule cell and molecular layers. In the rabbit cerebellar cortex, slightly higher grain density was observed in the granule cell layer than in the molecular layer. In lobules IX and X and in the hemisphere of X, the Purkinje cell layer was most densely labeled; parasagittal columns of very high grain density were present over the molecular layer of several cortical regions, including lobules, I, II, III, IV, V, IX, X, and the hemispheres of IX and X. Since muscarinic receptors have previously been found on blood vessels, there is a possibility that some proportion of receptor labeling may be localized to these structures. Microvessels and capillaries in each of the species examined were more numerous in the granule cell layer than in the molecular layer and white matter. The distribution of blood vessels in many cerebellar lobules of mice, rats, and guinea pigs corresponded quite closely to the general distribution of [3H]QNB binding sites. Unique patterns of labeling in lobules IX and X were not accompanied by corresponding patterns of blood vessel distribution, however. In the mouse, there was a slight increase in muscarinic receptor density observed in the archicerebellum, with no corresponding increase in the density of blood vessels.(ABSTRACT TRUNCATED AT 400 WORDS)

Zonation in the rat cerebellar cortex: patches of high acetylcholinesterase activity in the granular layer are congruent with Purkinje cell compartments

The rat cerebellar cortex is built from parasagittally arranged modules with topographically ordered afferent and efferent projections. The intrinsic organization of the cerebellum is revealed by immunocytochemical staining with monoclonal antibody, mabQ113. In the cerebellum, mabQ113 recognizes a polypeptide epitope that is restricted to a subset of Purkinje cells. Antigenic Purkinje cells are clustered to form a complex pattern of parasagittal compartments. Several biochemical markers reveal a superficially similar organization of the cortex, and so it is important to determine how many independent maps are present. This report compares the mabQ113 antigen display to the patchy distribution of acetylcholinesterase (AChE). In the granular layer and the white matter of the adult cerebellar cortex there is a patchy AChE staining that includes both the hemispheres and the vermis. The staining is often not sharply resolved cytologically, but seems to be associated primarily with the synaptic glomeruli. The boundaries of these granular layer patches in the vermis correspond to the mabQ113+/mabQ113- boundaries of the overlying Purkinje cell compartments. Thus, AChE and mabQ113 antigen share a common compartmentation both in the vermis, and in the hemispheres. Both mabQ113 and AChE distributions develop postnatally in the cerebellar cortex. At birth (PO) there is neither AChE activity nor mabQ113 immunoreactivity. Both staining patterns emerge during the second postnatal week. In the vermis at P10, there is AChE activity in the granular layer and white matter, and the distribution is already patchy despite the absence of synaptic glomeruli. At the same age the mabQ113 immunoreactivity is found in all Purkinje cells rather than a subset, and the band pattern has yet to mature. There is also transient AChE staining of Purkinje cell somata and dendrites. The AChE patches clarify between P10 and P20 along with the appearance of the synaptic glomeruli and the development of differential mabQ113 staining, but there is no reason to believe that the two are causally linked. In contrast to the cerebellar cortex, AChE staining in the cerebellar nuclei matures very early and at P0 the activity is already high. Zones of high and low AChE activity are seen in all the cerebellar nuclei and may be related to the distribution of the terminal fields of the different Purkinje cell populations.(ABSTRACT TRUNCATED AT 400 WORDS)

Topographic and zonal organization of the olivocerebellar projection in the reeler mutant mouse

The organization of the olivocerebellar projection in the homozygous reeler mouse (rl/rl) was studied with the use of microinjections of 3H-leucine in different regions of the inferior olivary complex (IO) or horseradish peroxidase conjugated with wheat germ agglutinin (WGA-HRP) into medial, intermediate, or lateral regions of the reeler cerebellum. The purpose of this investigation was to determine the pattern of termination of olivocerebellar climbing fibers (CFs) in the cerebellum via an anterograde tracing technique, and to determine the topographic organization of the olivocerebellar projection via both anterograde and retrograde methods. The inferior olive injections were made via the ventral (i.e., retropharygeal) approach to the IO to minimize diffusion into other brainstem precerebellar nuclei and thus to ensure accurate well-restricted, injection sites. Labeled CF terminals were seen in both the superficial Purkinje cell (PC) layer (normally positioned PCs) and around PCs in the granular layer and central masses (ectopic PCs). The pattern of labeling is suggestive of orthogonal organization, in that vertical columns of cells are labeled. This is especially apparent in the medial PC group, where at least three bands are identified. Within an orthogonal band, CF terminals are seen around both superficial and deep Purkinje cells. Our data indicate that olivocerebellar topography is generally similar in reeler and normal mice despite severe abnormalities in target cell position in the reeler. The medial cerebellar region receives input from the caudal two-fifths of the medial accessory olive (MAO). The intermediate PC cluster receives input from more rostral portions of all three olivary divisions (MAO, principal olive [PO] and dorsal accessory olive [DAO] ), while rostral portions of MAO and PO project to the lateral cerebellum. These results indicate that the zonal organization of the olivocerebellar projection in the adult reeler exhibits a pattern generally similar to that seen in normal mice. This suggests that an afferent system can develop a normal organization despite having ectopic targets.

Parasagittal organization of the rat cerebellar cortex: direct correlation between antigenic Purkinje cell bands revealed by mabQ113 and the organization of the olivocerebellar projection

The Purkinje cells of the cerebellar cortex and the cortical afferent and efferent projections are organized into parallel parasagittal zones. The parasagittal organization is clearly revealed by immunocytochemistry with a monoclonal antibody, mabQ113. The mabQ113 antigen is confined to a subset of Purkinje cells that are clustered together to form an elaborate, highly reproducible pattern of bands and patches, interspersed with similar mabQ113- regions. The mabQ113+ territories have been classified into seven parasagittal bands (P1+-P7+) in each hemicerebellum. The degree of correspondence between the compartments revealed by the anterograde labeling of the olivocerebellar projection and by mabQ113 immunocytochemistry has been explored in the adult rat. Horseradish peroxide-wheat germ agglutinin conjugate was injected as an anterograde tracer into the inferior olivary complex. When the injection site did not encompass all the olive, an incomplete, patchy labeling of the molecular layer was seen in the cerebellar cortex. Labeled zones of the molecular layer were interrupted by unlabeled regions to give a pattern of parasagittal cortical bands. The positions of these bands were compared with the distribution of the mabQ113+ antigenic bands as seen on the two adjacent sections. Labeled climbing fibers were found to terminate on both mabQ113+ and mabQ113- Purkinje cell zones. The mabQ113+/mabQ113- boundaries and the bands of climbing fibers seen by using the anterograde tracer typically coincide. The one consistent exception is the midline band of mabQ113+ Purkinje cells, P1+. The normal olivocerebellar projection is exclusively contralateral and the climbing fiber projection to the paramedian vermis splits P1+ down the middle, implying that it consists of two adjacent mabQ113+ bands not separated by mabQ113-territory. It is likely that the climbing fiber projection to the cerebellar cortex and the distribution of the two Purkinje cell phenotypes share a common compartmental organization.

Topographical organization of olivocerebellar and corticonuclear connections in the rat--an WGA-HRP study: I. Lobules IX, X, and the flocculus

The organization of the olivocerebellar and corticonuclear relations for vermal lobules IX and X and the flocculus has been studied in the rat by using microinjections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). This axonal tracer allowed us to study simultaneously the olivocortical connections (revealed by retrograde transport) and corticonuclear connections (revealed by anterograde transport) from a single injection in the cerebellar cortex. The results indicate that four modules can be distinguished, each of which consists of a region of cerebellar cortex receiving afferents from a single small region of the inferior olive (IO) and sending efferents to one or several portions of the cerebellar nuclei and/or vestibular nuclei. The first module includes a medial part of lobule X as well as all the flocculus. It receives afferents from the dorsal cap (dc) and sends efferents to the small cell (s) zone of the dentate nucleus as well as to the medial vestibular (VM) nucleus and subnucleus y. The second module includes a medial parasagittal region located in lobules IX and X. It receives afferents from the ventrolateral outgrowth (vlo) and/or beta nucleus (vlo + beta nucleus) and sends efferents principally to the ventrolateral part of fastigial nucleus and to the superior vestibular (VS), inferior vestibular (VI), and VM nuclei. The third module includes a lateral parasagittal region in lobules IX and X. It receives afferents from the dorsomedial cell column (dmcc) of IO and sends efferents principally to the interpositus nucleus and subnucleus y. The fourth module includes the most lateral part of lobules IX and Xa. It receives afferents from the principal olive (PO) and sends efferents to the s zone of the dentate nucleus. These results are comparable to those obtained in the cat although a few differences are discussed.

Antigenic map of the rat cerebellar cortex: the distribution of parasagittal bands as revealed by monoclonal anti-Purkinje cell antibody mabQ113

Both anatomical and physiological mapping methods have revealed that the mammalian cerebellar cortex consists of a family of parasagittal bands of cells, each band with its own pattern of afferent and efferent axons. Monoclonal antibody mabQ113 recognizes an unknown polypeptide antigen that is confined to a subset of rat cerebellar Purkinje cells. Immunoreactive cells are arranged into parasagittal bands extending throughout the vermis and hemispheres. Expression of the Q113 epitope by individual Purkinje cells may not be all-or-nothing, since the bands tend to be more strongly stained in the vermis than the hemispheres. The band display is symmetrical about the midline and reproducible from individual to individual. Whole-mount immunocytochemistry and serial reconstruction reveal a median band of mabQ113+ Purkinje cells adjacent to the midline (P1+) and six other positive bands disposed symmetrically at either side (P2+ to P7+). Bands are distinct throughout most of the cortex but tend to fuse ventrally and caudally. There are two sources of interindividual differences. Firstly, most animals express supernumerary "satellite" bands in the vermis. Satellite bands are usually only one cell wide, are not bilaterally symmetrical, and differ in position and number from individual to individual. Secondly, the precise position of an individual band can differ, perhaps according to the variable cortical lobulation, for example, the position of P4+ in lobules VIII/IX and P6+ in lobule VII. While a scheme of parasagittal bands is a good description of the vermian organization, the distribution of mabQ113+ and mabQ113- Purkinje cells in the hemispheres may be better described as a checkerboard of antigenic patches.

Somatosensory representation of the cerebellar climbing fiber system in the rat

The climbing fiber responses of 542 Purkinje cells were isolated in the vermal and intermediate zones of lobules II to VI of the rat cerebellum. Mechanical stimulation successfully elicited 53% of the isolated climbing fiber responses, whereas the remaining units were unresponsive to any stimulation employed. Of the units elicited by the stimulation, 34% required cutaneous and 66% required deep stimulation. Some proportion of the representation of each body region required either cutaneous or deep stimulation. The hind-limb had the largest representation and accounted for 55% (160/288) of the units. In contrast, the forelimb was only represented by 10% of the units, the tail by 16%, the face by 11% and the remaining 6% of the units by surface regions of the spine, chest and abdomen. On the basis of their proportional representation of body regions, 3 different cortical areas were distinguished: (1) a medial vermis, which consisted predominantly of unresponsive units; (2) a lateral vermis, which included representations of the extremities, trunk and tail; and (3) the intermediate zone, where the only representation of the face was evident. Within each area, the representations formed a disjunctive pattern of irregularly shaped patches and areas of overlap. In comparison with the climbing fiber organization of the cat, the medial vermal unresponsive zone and the patch-like representations of various body surfaces in the rat were similar to the cat, but the proportional representation of various body surfaces and effective stimulus modality were different, which may reflect morphological and behavioral differences between the species.

Zonal organization of olivocerebellar projections to the uvula in rabbits

Olivocerebellar projections to the uvula were studied by means of retrograde axonal transport of horseradish peroxidase (HRP) in pigmented rabbits. The distribution pattern of labeled cells in the inferior olive was compared among cases following large- and microinjections of HRP into the uvula. Findings indicate topographically organized projections to longitudinally oriented zones. There are at least 6 zones in the rabbit's uvula. The caudal part of the nucleus beta projects contralaterally to a most medially located zone (caudal beta zone). The rostral part of the nucleus beta projects to a little more laterally located zone (rostral beta zone) at a distance of about 1 mm from the midline of the uvula. The caudolateral part of the MAO projects to a zone (caudolateral MAO zone) located laterally to the rostral beta zone. The dorsomedial cell column projects to a zone (dorsomedial cell column zone) located in the intermediate part of the uvula at about 2 mm from the midline. The rostrolateral part of the MAO projects to the most lateral zone (rostrolateral MAO zone) of the uvula. Finally, the ventral lamella of the PO projects to a zone (ventral lamella of PO zone) located between the rostrolateral MAO zone and the dorsomedial cell column zone.

A qualitative and quantitative light microscopic study of the inferior olivary complex of normal, reeler, and weaver mutant mice

In the normal mouse (+/+; +/rl) cerebellar Purkinje cells (PCs) are aligned in a monolayer and provide the main targets for incoming olivocerebellar climbing fibers (CF). In the neurological mutants, homozygous reeler (rl/rl), homozygous weaver (wv/wv) and heterozygous weaver (wv/+), cerebellar abnormalities exist in which many PCs are either missing or displaced. Therefore, it is of interest of determine if the inferior olivary complex (IO) in these mutants is also abnormal. This report concerns results obtained from a light microscopic study of the inferior olivary complex. Counts of IO cells revealed apparent differences in the IO in homozygous reeler when compared to normal littermates. Whereas in the normal mouse there are approximately 37,000 IO cells and clearly defined olivary subdivisions, the IO of the homozygous reeler has a 22.6% reduction in IO cells (mean = 28,770) and indistinct borders between the major olivary subdivisions. With regard to the heterozygous and homozygous weaver, surprisingly the IO morphology and cell numbers are similar to that of the wildtype mouse even though the animals have only 86% (wv/+, mean = 158,155) and 72% (wv/wv, mean = 131,882), respectively, of the normal numbers of PCs (+/+, mean = 183,857). Purkinje cell counts revealed that the midline vermal region is the most affected area in the cerebellum in wv/+ and wv/wv whereas counts in the lateral hemisphere are near normal. The PC/IO ratio in the homozygous weaver is approximately 3:1 as compared to 5:1 in the wildtype mouse. Recent electrophysiological findings in wv/wv indicate that PCs are multiply innervated by CFs. Since a transient phase of multiple innervation is normal in the immature rat, the situation in the adult homozygous weaver may represent a retention of this immature state. A factor which may play a role in this is the loss of parallel fiber (PF)-PC synapses resulting from massive postnatal granule cell death. An hypothesis suggesting an intrinsic PC time-dependent mutant gene effect is presented to account for the differences in the loss of Purkinje cells between wv/wv and wv/+ and between different regions of the cerebellum.

Architectonic and hodological organization of the cerebellum in reeler mutant mice

The architectonic and hodologic organization of the reeler cerebellum has been studied by means of immunohistochemistry, general cell and fiber stains and by horseradish peroxidase and autoradiographic tracing methods. Malposition of Purkinje cells, which varies in degree, is the most salient architectonic anomaly of the mutant cerebellum. Mapping the distribution of Purkinje cells is facilitated by a monoclonal antibody which selectively stains neurons of this class in the cerebellum. Although some Purkinje cells form a normal monolayer, most lie in heterotopic positions within or below the granule cell layer. The major contingent is segregated in subcortical masses in the depths of the cerebellum. Fiber bundles continuous with the cerebellar peduncles run in septa between the subcortical Purkinje cell masses. The distribution of Purkinje cell masses as well as the roof nuclei and areas of normal cortex and fiber bundles are identical from animal to animal. These consistent architectonic variations serve to partition the reeler cerebellum into 7 sagittally oriented compartments: one medial, two intermediate, two lateral and two additional lateral lobular appendages which may correspond to paraflocculus and/or flocculus of the normal cerebellum. The topography of the reeler olivocerebellar, or climbing fiber, system is normal in that the caudal-to-rostral axis of the olivary complex maps onto the medial-to-lateral axis of the contralateral hemicerebellum. The climbing fiber projection in reeler, like that of the normal animal, appears to be organized in parasagittal strips. In the mutant, mossy fibers from the pons and spinal cord project respectively to the lateral and medial cerebellar fields, and overlap in the intermediate compartment. They thus invest different and to a large extent complementary cerebellar territories, which approximate the architectonic divisions. This segregation of the two principal mossy fiber systems is not so marked in the normal cerebellum. In terms of laminar distribution, the pontine projection is distributed principally to the granule cell stratum in the mutant. The reeler spinocerebellar afferents, by contrast, project not only to the granule cell layer but also to the heterotopic Purkinje cells. The present observations suggest that the primary defect in the reeler cerebellum is malposition of Purkinje cells. As appears to be the case during development of the forebrain in reeler, the mutation may affect the terminal phase of migration of Purkinje cells in the cerebellum.(ABSTRACT TRUNCATED AT 400 WORDS)