Chemical heterogeneity in cerebellar Purkinje cells: existence and coexistence of glutamic acid decarboxylase-like and motilin-like immunoreactivities

Localization of AMPA, kainate, and NMDA receptor mRNAs in the pigeon cerebellum

In the present study, we investigated the location of mRNAs for three types of ionotropic glutamate receptors (iGluRs) in the pigeon cerebellum and then compared the results with those of mammals. The following nine iGluRs subunits were analyzed by in situ hybridization: AMPA receptors (GluA1, GluA2, GluA3, and GluA4), kainate receptors (GluK1, GluK2, and GluK4), and NMDA receptors (GluN1 and GluN2A). Subunit hybridization revealed expression in different cell types of the cerebellar cortex: Purkinje cells expressed most subunits, including AMPA receptors (GluA1, GluA2, and GluA3), kainate receptors (GluK1 and GluK4), and NMDA receptors (GluN1); granule cells expressed four subunits of kainate (GluK1 and GluK2) and NMDA receptors (GluN1 and GluN2A); stellate and basket cells expressed GluK1, GluK2, and GluN1; Golgi cells expressed GluA1, GluA3, and GluN1; and Bergmann glial cells expressed only AMPA receptors (GluA2 and GluA4). Cerebellar nuclei showed no AMPA subunit signals, whereas kainate and NMDA receptors were observed in the five cerebellar nuclei divisions (CbL, CbMic, CbMim, CbMin, and CbMvm). The five divisions showed weak expression of GluK1, GluK2, and GluN2A; moderate to intense expression of GluK4; and intense expression of GluN1. These results demonstrate that in pigeons the cerebellar cortex expresses AMPA, kainate, and NMDA receptors, while the cerebellar nuclei express kainate and NMDA receptors. Taken together, these findings provide anatomical data for further analysis of the functions of iGluR-expressing neurons in glutamatergic circuits of the avian cerebellum.

The functional anatomy of the cerebrocerebellar circuit: A review and new concepts

The cerebrocerebellar circuit is a feedback circuit that bidirectionally connects the neocortex and the cerebellum. According to the classic view, the cerebrocerebellar circuit is specifically involved in the functional regulation of the motor areas of the neocortex. In recent years, studies carried out in experimental animals by morphological and physiological methods, and in humans by magnetic resonance imaging, have indicated that the cerebrocerebellar circuit is also involved in the functional regulation of the nonmotor areas of the neocortex, including the prefrontal, associative, sensory and limbic areas. Moreover, a second type of cerebrocerebellar circuit, bidirectionally connecting the hypothalamus and the cerebellum, has been detected, being specifically involved in the regulation of the hypothalamic functions. This review analyzes the morphological features of the centers and pathways of the cerebrocerebellar circuits, paying particular attention to their organization in different channels, which separately connect the cerebellum with the motor areas and nonmotor areas of the neocortex, and with the hypothalamus. Actually, a considerable amount of new data have led, and are leading, to profound changes on the views on the anatomy, physiology, and pathophysiology of the cerebrocerebellar circuits, so much they may be now considered to be essential for the functional regulation of many neocortex areas, perhaps all, as well as of the hypothalamus and of the limbic system. Accordingly, clinical studies have pointed out an involvement of the cerebrocerebellar circuits in the pathophysiology of an increasing number of neuropsychiatric disorders.

Prenatal exposure to sodium valproate alters androgen receptor expression in the developing cerebellum in a region and age specific manner in male and female rats

Valproic acid (VPA) is an anti-epileptic drug with teratogenicity activity that has been related to autism. In rodents, exposure to VPA in utero leads to brain abnormalities similar than those reported in the autistic brain. Particularly, VPA reduces the number of Purkinje neurons in the rat cerebellum parallel to cerebellar abnormalities found in autism. Thus, we injected pregnant females on embryonic day 12 either with VPA (600mg/kg, i.p.) or 0.9% saline solution and obtained the cerebellum from their offspring at different postnatal time points. Testosterone has been linked to autism and plays an important role during brain development. Therefore, we identified and analyzed the androgen receptor (AR) by immunohistochemistry and densitometry, respectively. We found VPA decreases AR density in the superficial Purkinje layer only in cerebellar lobule 8 at PN7, but increased it at PN14 compared to control in males. In females, VPA decreased AR density in the superficial Purkinje layer in cerebellar lobule 6 at PN14, but increased it in lobule 9 at the same time point. No differences were found in the deep Purkinje layer of any cerebellar lobule in terms of AR density neither in males nor females. We additionally found a particular AR density decreasing in both superficial and deep regions across development in the majority of cerebellar lobules in males, but in all cerebellar lobules in females. Thus, our results indicate that VPA disrupts the AR ontogeny in the developing cerebellum in an age and region specific manner in male and female rats. Future epigenetic studies including the evaluation of histone deacetylases (HDAC's) might shed light these results as HDAC's are expressed by Purkinje neurons, interact with the AR and are VPA targets. This work contributes to the understanding of the cerebellar development and it might help to understand the role of the cerebellum in neurodevelopmental disorders such as autism.

The role of GABAB receptors in the vestibular oculomotor system in mice

Systemic administration of a gamma-amino butyric acid type B (GABAB) receptor agonist, baclofen, affects various physiological and psychological processes. To date, the effects on oculomotor system have been well characterized in primates, however those in mice have not been explored. In this study, we investigated the effects of baclofen focusing on vestibular-related eye movements. Two rotational paradigms, i.e. sinusoidal rotation and counter rotation were employed to stimulate semicircular canals and otolith organs in the inner ear. Experimental conditions (dosage, routes and onset of recording) were determined based on the prior studies exploring the behavioral effects of baclofen in mice. With an increase in dosage, both canal and otolith induced ocular responses were gradually affected. There was a clear distinction in the drug sensitivity showing that eye movements derived from direct vestibulo-ocular reflex pathways were relatively unaltered, while the responses through higher-order neural networks in the vestibular system were substantially decreased. These findings were consistent with those observed in primates suggesting a well-conserved role of GABAB receptors in the oculomotor system across frontal-eyed and lateral-eyed animals. We showed here a previously unrecognized effect of baclofen on the vestibular oculomotor function in mice. When interpreting general animal performance under the drug, the potential contribution of altered balance system should be taken into consideration.

Heterogeneity of calretinin expression in the avian cerebellar cortex of pigeons and relationship with zebrin II

The cerebellar cortex has a fundamental parasagittal organization that is reflected in the physiological responses of Purkinje cells, projections of Purkinje cells, afferent inputs from climbing and mossy fibres and the expression of several molecular markers. The most thoroughly studied of these molecular markers is zebrin II (ZII; a.k.a. aldolase C). ZII is differentially expressed in Purkinje cells, resulting in a pattern of sagittal stripes of high expression (ZII+ve) interdigitated with stripes of little or no expression (ZII-ve). The calcium binding protein calretinin (CR) is expressed heavily in mossy fibres terminating throughout the cerebellar cortex, but whether CR is heterogeneously expressed in parasagittal stripes, like ZII, is unknown. In this study, we examined CR expression in the cerebellum of pigeons and compared it to that of ZII. CR was expressed heavily in the granule layer in mossy fibres and their terminal rosettes. Moreover, CR is expressed heterogeneously in the granule layer such that there are sagittal stripes of heavy CR labelling (CR+ve) alternating with stripes of weaker labelling (CR-ve). The CR heterogeneity is most notable in folium IXcd and folia II-IV in the anterior lobe. In the anterior lobe, the central CR+ve stripe spanning the midline is aligned with the central ZII+ve stripe, whereas the other CR+ve stripes are aligned with the ZII-ve stripes. In IXcd, the CR+ve stripes are aligned with the ZII+ve stripes. This combination of aligned and unaligned CR+ve stripes, relative to ZII+ve stripes, differs from that of parvalbumin and other neurochemical markers, but the functional consequences of this is unclear. With respect to the posterior lobe, we suggest that the CR+ve mossy fibres to IXcd originate in two retinal recipient nuclei that are involved in the processing of optic flow.

Irisin-immunoreactivity in neural and non-neural cells of the rodent

Irisin is a recently identified myokine secreted from the muscle in response to exercise. In the rats and mice, immunohistochemical studies with an antiserum against irisin peptide fragment (42-112), revealed that irisin-immunoreactivity (irIRN) was detected in three types of cells; namely, skeletal muscle cells, cardiomyocytes, and Purkinje cells of the cerebellum. Tissue sections processed with irisin antiserum pre-absorbed with the irisin peptide (42-112) (1 μg/ml) showed no immunoreactivity. Cerebellar Purkinje cells were also immunolabeled with an antiserum against fibronectin type II domain containing 5 (FNDC5), the precursor protein of irisin. Double-labeling of cerebellar sections with irisin antiserum and glutamate decarboxylase (GAD) antibody showed that nearly all irIRN Purkinje cells were GAD-positive. Injection of the fluorescence tracer Fluorogold into the vestibular nucleus of the rat medulla retrogradely labeled a population of Purkinje cells, some of which were also irIRN. Our results provide the first evidence of expression of irIRN in the rodent skeletal and cardiac muscle, and in the brain where it is present in GAD-positive Purkinje cells of the cerebellum. Our findings together with reports by others led us to hypothesize a novel neural pathway, which originates from cerebellum Purkinje cells, via several intermediary synapses in the medulla and spinal cord, and regulates adipocyte metabolism.

Heterotrimeric guanosine triphosphate-binding protein-coupled modulatory actions of motilin on K+ channels and postsynaptic γ-aminobutyric acid receptors in mouse medial vestibular nuclear neurons

Some central nervous system neurons express receptors of gastrointestinal hormones, but their pharmacological actions are not well known. Previous anatomical and unit recording studies suggest that a group of cerebellar Purkinje cells express motilin receptors, and motilin depresses the spike discharges of vestibular nuclear neurons that receive direct cerebellar inhibition in rats or rabbits. Here, by the slice-patch recording method, we examined the pharmacological actions of motilin on the mouse medial vestibular nuclear neurons (MVNs), which play an important role in the control of ocular reflexes. A small number of MVNs, as well as cerebellar floccular Purkinje cells, were labeled with an anti-motilin receptor antibody. Bath application of motilin (0.1 μm) decreased the discharge frequency of spontaneous action potentials in a group of MVNs in a dose-dependent manner (K(d) , 0.03 μm). The motilin action on spontaneous action potentials was blocked by apamin (100 nm), a blocker of small-conductance Ca(2+) -activated K(+) channels. Furthermore, motilin enhanced the amplitudes of inhibitory postsynaptic currents (IPSCs) and miniature IPSCs, but did not affect the frequencies of miniature IPSCs. Intracellular application of pertussis toxin (PTx) (0.5 μg/μL) or guanosine triphosphate-γ-S (1 mm) depressed the motilin actions on both action potentials and IPSCs. Only 30% of MVNs examined on slices obtained from wild-type mice, but none of the GABAergic MVNs that were studied on slices obtained from vesicular γ-aminobutyric acid transporter-Venus transgenic mice, showed such a motilin response on action potentials and IPSCs. These findings suggest that motilin could modulate small-conductance Ca(2+) -activated K(+) channels and postsynaptic γ-aminobutyric acid receptors through heterotrimeric guanosine triphosphate-binding protein-coupled receptor in a group of glutamatergic MVNs.

Erythromycin inhibited glycinergic inputs to gastric vagal motoneurons in brainstem slices of newborn rats

BACKGROUND

Motilin has been known to stimulate the motility of digestive organs peripherally via activation of motilin receptors located at gastrointestinal (GI) cholinergic nerve endings and/or smooth muscle cells. Recent studies have indicated that motilin may also promote GI motility via actions in the central nervous system; however the sites of action and the mechanisms are not clear yet. The present study aimed to test the hypothesis that motilin receptor agonist erythromycin alters the synaptic inputs of preganglionic gastric vagal motoneurons (GVMs) located in the dorsal motor nucleus of the vagus (DMV).

METHODS

Gastric vagal motoneurons were retrogradely labeled by fluorescent tracer from the stomach wall of newborn rats. Fluorescently labeled GVMs in DMV were recorded using whole-cell patch-clamp in brainstem slices and the effects of motilin receptor agonist erythromycin on the synaptic inputs were examined.

KEY RESULTS

Erythromycin (100 nmol L(-1), 1 μmol L(-1), 10 μmol L(-1)) significantly inhibited the frequency of glycinergic spontaneous inhibitory postsynaptic currents (sIPSCs) of GVMs and significantly inhibited the amplitude at the concentration of 10 μmol L(-1). These responses were prevented by GM-109, a selective motilin receptor antagonist. In the pre-existence of tetradotoxin (TTX, 1 μmol L(-1)), erythromycin (10 μmol L(-1)) caused significant decreases of the glycinergic miniature inhibitory postsynaptic currents (mIPSCs), in both the frequency and the amplitude. However, erythromycin (10 μmol L(-1)) didn't cause significant changes of the GABAergic sIPSCs.

CONCLUSIONS & INFERENCES

Erythromycin selectively inhibits the glycinergic inputs of GVMs.

Regional (14C) 2-deoxyglucose uptake during forelimb movements evoked by rat motor cortex stimulation: pons, cerebellum, medulla, spinal cord, muscle

Electrical stimulation of the right forelimb motor (MI) sensory (SI) cortex in normal, adult rats produced repetitive left forelimb movements. Regions of increased (14C) 2-deoxyglucose (2DG) uptake were mapped auto-radiographically during these movements. MI stimulation activated the ipsilateral reticular tegmental pontine nucleus (RTP) and the middle (rostral-caudal) third of the pontine nuclei including pyramidal (P), medial (POM), ventral (POV), and lateral (POL) pontine nuclei. The ipsilateral inferior olivary complex was activated including dorsal accessory olive (DAO), principal olive (PO), and medial accessory olive (MAO). The contralateral lateral reticular (LR) nucleus and nucleus cuneatus (CU) were activated. Lateral vermal, paravermal, and hemispheric portions of the contralateral cerebellum were also activated. Parts of vermian lobules IV, V, VI, VII, and VIII, and lobulus simplex, crus I, crus II, paramedian lobule, and copula pyramidis were activated. Granule cell layers were activated much more than molecular layers. Discrete microzones of high granule cell 2DG uptake alternated with zones of low uptake in left paramedian lobule and copula pyramidis and may correlate with the fractured cerebellar somatotopy described physiologically by Welker and his associates. Portions of the left lateral and interpositus nuclei were metabolically activated. Medial portions of laminae I-VI were activated in the dorsal horn of cervical spinal cord. The 2DG uptake was either unchanged or decreased in the ventral horn. Thoracic and lumbar spinal cord were not activated. Monsynaptic MI and SI connections to P, POM, POV, POL, RTP, DAO, PO, MAO, LR, CU, and spinal cord could account for activation of those structures. However, there are no direct MI or SI connections to the deep cerebellar nuclei, the cerebellar hemisphere, or the muscles. Activation of these structures must be due to activation of polysynaptic pathways, sensory feedback from the moving forelimb, or both. The present experiments cannot distinguish these possibilities. Comparison of the regions activated during forelimb MI stimulation (FLMIS) to those activated during vibrissae MI stimulation (VMIS) suggests that the pontine nuclei, cerebellar hemisphere, and possibly the deep cerebellar nuclei are somatotopically organized. RTP, LR, CU, and spinal cord were activated during FLMIS but were not activated during VMIS. The failure to activate the ventral horn of cervical spinal cord may be due to known inhibition of alpha-motor neurons during motor cortex stimulation.

Distribution and electrophysiological effects of motilin in Purkinje cells

Evidence exists that motilin immunoreactivity is highly expressed in Purkinje cells. In this study, immunohistochemistry and whole-cell patch-clamp recording were performed to investigate the spatial distribution and electrophysiological effects of motilin receptors in the cerebellum. We show here that motilin receptors are strongly expressed in Purkinje cells of the human and rat cerebellum. Motilin at 10 nM depolarized Purkinje cells of the rat cerebellum, and this was mimicked by the motilin receptor agonist erythromycin. The depolarization evoked by motilin persisted in the presence of tetrodotoxin, glutamate and gamma-amino-n-butyric acid receptor antagonists, indicating that motilin excited the Purkinje cells by activating the receptor expressed on the neurons recorded. We suggest that motilin may serve specific neural functions in the cerebellum.

Purkinje cell compartmentation as revealed by Zebrin II expression in the cerebellar cortex of pigeons (Columba livia)

Purkinje cells in the cerebellum express the antigen zebrin II (aldolase C) in many vertebrates. In mammals, zebrin is expressed in a parasagittal fashion, with alternating immunopositive and immunonegative stripes. Whether a similar pattern is expressed in birds is unknown. Here we present the first investigation into zebrin II expression in a bird: the adult pigeon (Columba livia). Western blotting of pigeon cerebellar homogenates reveals a single polypeptide with an apparent molecular weight of 36 kDa that is indistinguishable from zebrin II in the mouse. Zebrin II expression in the pigeon cerebellum is prominent in Purkinje cells, including their dendrites, somata, axons, and axon terminals. Parasagittal stripes were apparent with bands of Purkinje cells that strongly expressed zebrin II (+ve) alternating with bands that expressed zebrin II weakly or not at all (-ve). The stripes were most prominent in folium IXcd, where there were seven +ve/-ve stripes, bilaterally. In folia VI-IXab, several thin stripes were observed spanning the mediolateral extent of the folia, including three pairs of +ve/-ve stripes that extended across the lateral surface of the cerebellum. In folium VI the zebrin II expression in Purkinje cells was stronger overall, resulting in less apparent stripes. In folia II-V, four distinct +ve/-ve stripes were apparent. Finally, in folia I (lingula) and X (nodulus) all Purkinje cells strongly expressed zebrin II. These data are compared with studies of zebrin II expression in other species, as well as physiological and neuroanatomical studies that address the parasagittal organization of the pigeon cerebellum.

Cerebellar cortical molecular layer inhibition is organized in parasagittal zones

Molecular layer inhibitory interneurons generate on-beam and off-beam inhibition in the cerebellar cortex that is hypothesized to control the timing and/or spatial patterning of Purkinje cell discharge. On- and off-beam inhibition has been assumed to be spatially uniform and continuous within a folium. Using flavoprotein autofluorescence optical imaging in the mouse cerebellar cortex in vivo, this study demonstrates that the inhibition evoked by parallel fiber and peripheral stimulation results in parasagittal bands of decreases in fluorescence that correspond to zebrin II-positive bands. The parasagittal bands of decreased fluorescence are abolished by GABA(A) antagonists and reflect the activity of molecular layer interneurons on their targets. The same banding pattern was observed using Ca2+ imaging. The bands produce spatially specific decreases in the responses to peripheral input. Therefore, molecular layer inhibition is compartmentalized into zebrin II parasagittal domains that differentially modulate the spatial pattern of cerebellar cortical activity.

Effects of norepinephrine depletion in rats during cerebral post-ischemic reperfusion

The present paper reports the effects of norepinephrine depletion in rats, after treatment with N-(2-chloroethyl)-N-ethyl 2-bromobenzylamine (DSP-4) neurotoxin, on partial cerebral ischemia and reperfusion. Histological observations made under experimental conditions of noradrenergic (NA)-depletion demonstrated that neuronal lesions were not exacerbated; in fact, in DSP-4-treated ischemic animals, a minor number of neurons appeared damaged. Our results suggest that neuronal recovery after post-ischemic reperfusion is not affected by NA-depletion. DSP-4 neurotoxin does not induce 5-hydroxy-triptamine (5-HT) depletion.

Antigenic compartmentation of the primate and tree shrew cerebellum: a common topography of zebrin II in Macaca mulatta and Tupaia belangeri

Despite the apparent uniformity in cellular composition of the adult cerebellar cortex, functional, anatomical, mutational and molecular maps all reveal a complex topography underlying the relatively simple architecture. In particular, zebrin II, a polypeptide antigen identified as aldolase C, is restricted to a subset of Purkinje cells that form a symmetrical and reproducible array of zones and stripes. The vermis of the well-studied rodent cerebellar cortex is divided into four transverse zones--anterior ( approximately lobules I-V), central ( approximately lobules VI and VII), posterior ( approximately lobule VIII) and nodular ( approximately lobules IX and X). Each transverse zone is further subdivided mediolaterally into parasagittal stripes. To gain insight into the evolution of cerebellar compartmentation, the pattern of zebrin II expression has been compared between the primate Macaca mulatta and the tree shrew Tupaia belangeri, and the results related to previous findings from other species. Although the somata of most Purkinje cells in the Macaca cerebellum express zebrin II, parasagittal stripes can still be delineated owing to the alternating high and low zebrin II immunoreactivity in the dendrites. In the macaque vermis, a complex set of zebrin II parasagittal compartments is found in all transverse zones. Unlike in rodents, in which uniform expression domains interrupt heterogeneous zones, zebrin II parasagittal stripes in the macaque cerebellum are seen throughout the vermis. In Tupaia, the parasagittal pattern of zebrin II expression also reveals a striking array of stripes in all lobules. The data suggest that cerebellar compartmentation in Tupaia belangeri more closely resembles that of primates than it does rodents or lagomorphs.

Development of cerebellar modules: extrinsic control of late-phase zebrin II pattern and the exploration of rat/mouse species differences

The vertebrate cerebellum is divided into a characteristic set of 13 parasagittal "bands" or modules that are revealed in many different domains-ranging from patterns of gene and protein expression to the organization of afferent input. We have used the expression of Zebrin II/aldolase C in Purkinje cells as a marker of these bands and have discovered several new features of their regulation. We find that appearance of the banded expression of aldolase C during development differs between rat and mouse. In agreement with previous reports there is, in rat, a transient period during which all Purkinje cells are positive for aldolase C expression. By contrast, in mouse, the pattern emerges in its adult (banded) form from the earliest postnatal times. This species difference is found in both mRNA and protein expression. There also appears to be a transition that occurs in vivo between postnatal days 8 and 10. Slice cultures established from cerebella at the younger age do not develop a complete banding pattern, even after 6 days in culture. Slice cultures established from postnatal day 10 mice develop the full pattern within 2 days. This difference cannot be overcome by manipulating the levels of neuronal activity in the cultures. Thus some event must occur in vivo that "releases" the adult pattern and allows it to be realized in the more artificial situation of the slice culture. Taken together the results offer a more complete picture of the regulation of the aldolase C gene in cerebellar Purkinje cells and suggest important species differences in its developmental expression pattern.

Expression and possible role of neuronal calcium sensor-1 in the cerebellum

Neuronal calcium sensor-1 (NCS-1) is a member of EF-hand calcium-binding protein superfamily, which is considered to modulate synaptic transmission and plasticity. In this mini-review, we first summarize distribution of NCS-1 in the cerebellum. NCS-1 is mainly detected in postsynaptic sites, such as somata and dendrites of Purkinje cells, stellate/basket cells and granule cells. In addition, GABAergic inhibitory stellate/basket cell axon terminals also contain NCS-1. Secondly, we describe cerebellar compartmentation defined by NCS-1. The NCS-1 immunostaining displayed characteristic parasagittal-banding pattern in the Purkinje cell layer and molecular layer, whereas there were no apparent bands in the granule cell layer. The alternating positively and negatively NCS-1-labeled Purkinje cell clusters contributed to this cerebellar compartmentation. In contrast, stellate/basket cells were uniformly NCS-1-positive throughout the cerebellum. Interestingly, NCS-1 and zebrin II exhibited a similar parasagittal-banding pattern. But it is noteworthy that NCS-1-negative/zebrin II-positive Purkinje cell clusters were detected selectively in anterior lobule vermis and paraflocculus. These results suggest that NCS-1 defines a novel pattern of cerebellar cortical compartmentation. Lastly, we describe recent data suggesting some relationship between NCS-1 and cerebellar long-term depression-related molecules, and discuss the possible role of NCS-1 in the cerebellum.

Compartmentation of the mouse cerebellar cortex by neuronal calcium sensor-1

Neuronal calcium sensor-1 (NCS-1) is a member of the EF-hand calcium-binding protein superfamily, which is considered to modulate synaptic transmission and plasticity. The detailed distribution of NCS-1 was analyzed in the mouse cerebellar cortex. In coronal sections, the NCS-1 immunostaining displayed characteristic parasagittal banding pattern in the Purkinje cell layer and molecular layer, while there were no apparent bands in the granule cell layer. The alternating positively and negatively NCS-1-labeled Purkinje cell clusters contributed to this cerebellar compartmentation. In contrast, stellate-basket cells were uniformly NCS-1-positive throughout the cerebellum. Immunofluorescent double staining showed that NCS-1 and zebrin II exhibited a similar parasagittal banding pattern. Then, we performed mapping of NCS-1- and/or zebrin II-labeled Purkinje cell somata using seven sequential coronal sections. NCS-1-positive/zebrin II-positive Purkinje cell clusters were seen throughout the cerebellum, but NCS-1-positive/zebrin II-negative Purkinje cells were exceedingly rare. On the other hand, NCS-1-negative/zebrin II-positive Purkinje cell clusters were found in anterior lobule vermis and paraflocculus, whereas they were rarely seen in posterior lobules. The digitized quantitative analysis showed close relationship between NCS-1 and zebrin II immunoreactivity in the molecular layer. The correspondence between NCS-1 and zebrin II demonstrated here indicates a novel anteroposterior difference of cerebellar compartmentation and provides fundamental information of cerebellar organization.

Acrylamide neuropathy. I. Spatiotemporal characteristics of nerve cell damage in rat cerebellum

Based on evidence from morphometric studies of PNS, we suggested that acrylamide (ACR)-induced distal axon degeneration was a secondary effect related to duration of exposure [Toxicol. Appl. Pharmacol. 151 (1998) 211]. To test this hypothesis in CNS, the cupric-silver stain method of de Olmos was used to define spatiotemporal characteristics of nerve somal, dendritic, axonal and terminal degeneration in rat cerebellum. Rats were exposed to ACR at either 50 mg/kg per day (i.p.) or 21 mg/kg per day (p.o.) and at selected times (i.p. = 5, 8 and 11 days; p.o. = 7, 14, 21, 28 and 38 days) brains were removed and processed for silver staining. Results demonstrate that intoxication at the higher ACR dose-rate produced early (day 5) and progressive degeneration of Purkinje cell dendrites in cerebellar cortex. Nerve terminal degeneration occurred concurrently with somatodendritic argyrophilia in cerebellar and brainstem nuclei that receive afferent input from Purkinje neurons. Relatively delayed (day 8), abundant axon degeneration was present in cerebellar white matter but not in cortical layers or in tracts carrying afferent fibers (cerebellar peduncles) from other brain nuclei. Axon argyrophilia coincided with the appearance of perikaryal degeneration, which was selective for Purkinje cells since silver impregnation of other cerebellar neurons was not evident in the different cortical layers or cerebellar nuclei. Intoxication at the lower ACR dose-rate produced simultaneous (day 14) dendrite, axon and nerve terminal argyrophilia and no somatic Purkinje cell degeneration. The spatiotemporal pattern of dendrite, axon and nerve terminal loss induced by both ACR dose-rates is consistent with Purkinje cell injury. Injured neurons are likely to be incapable of maintaining distal processes and, therefore, axon degeneration in the cerebellum is a component of a "dying-back" process of neuronal injury. Because cerebellar coordination of somatomotor activity is mediated solely through efferent projections of the Purkinje cell, injury to this neuron might contribute significantly to gait abnormalities that characterize ACR neurotoxicity.

Demonstration of a functional motilin receptor in TE671 cells from human cerebellum

BACKGROUND

Our laboratory has described the presence of motilin receptors in the rabbit cerebellum. We discovered its presence in the human TE671 cell line, which is of cerebellar origin.

METHODS

Cytosolic Ca(2+) fluxes were monitored on a confocal microscope in cells loaded with Indo-1 and stimulated with motilin under various conditions. Binding studies were performed with 125I-[Nle(13)]porcine motilin. Using primers, PCR for the motilin receptor was performed.

RESULTS

Cells responded to motilin after 45+/-20 s. At different concentrations of motilin (10(-8), 10(-7), 10(-6.5), 10(-6) and 10(-5) M) the percentage of responding cells was 0+/-0, 0.6+/-1.5, 4.9+/-4.7, 21.7+/-15 and 35.7+/-12, respectively. The response was blocked by the motilin antagonists [Phe(3), Nle(13)]po-motilin (0.8+/-1.8%) and GM-109 (0.0+/-0.0%) and mimicked by the agonist ABT-229 (23.6+/-15%). After stimulation with motilin, ABT-229 or [Phe(3),Leu(13)]po-motilin, but not with the antagonist GM-109, cells were desensitized. The response to motilin persisted in Ca(2+)-free solution (22.8+/-14.7%), was not affected by nifedipine (44+/-11%) but was abolished by incubation with thapsigargin (0+/-0%). Neither ryanodine, nor a previous stimulation with caffeine (0+/-0%) in Ca(2+)-free Krebs, nor both could block the response to motilin (28, 32.0+/-5.7, 41.3+/-6.1%, respectively). Binding studies revealed two binding sites for motilin, with a pK(d) of 8.9+/-0.05 and 6.11+/-0.61 (n=4). There were 100 times more low than high affinity receptors per cell. The presence of receptor mRNA was confirmed by PCR.

CONCLUSION

Functional motilin receptors are present in TE671 cells. The response requires intracellular IP(3)-sensitive Ca(2+) stores. These cells may serve as a model of the central motilin receptor.

Neurotransmitters, neuropeptides and calcium binding proteins in developing human cerebellum: a review

Many endogenous neurochemicals that are known to have important functions in the mature central nervous system have also been found in the developing human cerebellum. Cholinergic neurons, as revealed by immunoreactivities towards choline acetyltransferase or acetylcholinesterase, appear early at 23 weeks of gestation in the cerebellar cortex and deep nuclei. Immunoreactivities gradually increase until the first postnatal month. Enkephalin is localized in the developing cerebellum, initially in the fibers of the cortex and deep nuclei at 16-20 weeks and then also in the Purkinje cells, granule cells, basket cells and Golgi cells at 23 weeks onward. Another neuropeptide, substance P, is localized mainly in the fibers of the dentate nucleus from 9 to 24 weeks but substance P immunoreactivity declines thereafter. GABA, an inhibitory neurotransmitter of the central nervous system, starts to appear at 16 weeks in the Purkinje cells, stellate cells, basket cells, mossy fibers and neurons of deep nuclei. GABA expression is gradually upregulated toward term forming networks of GABA-positive fibers and neurons. Catecholaminergic fibers and neurons are also detected in the cortex and deep nuclei at as early as 16 weeks. Calcium binding proteins, calbindin D28K and parvalbumin, make their first appearance in the cortex and deep nuclei at 14 weeks and then their expression decreases toward term, while calretinin appears later at 21 weeks but its expression increases with fetal age. The above findings suggest that many neurotransmitters, neuropeptides and calcium binding proteins (1) appear early during development of the cerebellum; (2) have specific temporal and spatial expression patterns; (3) may have functions other than those found in the mature neural systems; and (4) may be able to interact with each other during early development.

Role of climbing fibers in determining the spatial patterns of activation in the cerebellar cortex to peripheral stimulation: an optical imaging study

The spatial patterns of activation in the rat cerebellar cortex evoked by ipsilateral face stimulation were mapped using optical imaging based on the pH sensitive dye, Neutral Red. The aims of the study were to characterize the optical responses evoked by peripheral stimulation and test the hypothesis that the resultant parasagittal banding is due to climbing fiber activation. In the anesthetized rat Crus I and II of the cerebellar cortex were stained with Neutral Red. Epi-fluorescent changes produced by a train of stimuli (5-10s and 4-20 Hz) to the ipsilateral face were monitored in time using a fast, high resolution charge-coupled device camera. The patterns of activation were quantified using a two-dimensional fast Fourier transform analysis that removed signals with high spatial frequencies and minimized the contribution of horizontal structural elements (i.e. blood vessels). The dominant spatial pattern of activation evoked by face stimulation was that of parasagittal bands. The bands were highly frequency-dependent and were elicited most strongly by stimulus frequencies in the range of 6-8 Hz. There was a large fall-off in the response for frequencies above and below. The optical signal evoked by face stimulation built up over a period of 10s and then gradually decayed. Within a folium the individual parasagittal bands exhibited some frequency and temporal specificity. Stimulation of the contralateral inferior olive also resulted in the activation of parasagittal bands with characteristics similar to the bands evoked by face stimulation, including a preferred stimulus frequency which peaked at 10 Hz. Injection of lidocaine into the contralateral inferior olive blocked the parasagittal bands evoked by ipsilateral face stimulation, while control injections of saline had no effect. The results confirm that a parasagittal banding pattern is a dominant feature of the functional architecture of the cerebellar cortex. The parasagittal banding pattern observed with Neutral Red is due primarily to the activation of climbing fiber afferents. The frequency tuning of the responses, with the preference for peripheral stimuli of 6-8 Hz, is in agreement with previous findings that the inferior olive is inherently rhythmic. These observations support the hypothesis that inferior olivary neurons are dynamically coupled into groups that activate parasagittal bands of Purkinje cells in the cerebellar cortex. The frequency tuning also supports the hypothesis that the climbing fiber system is involved with timing. Activation of this afferent system may require stimuli with appropriate frequency content and stimuli synchronized to the rhythmicity of the inferior olive.

Calcium signaling molecules in human cerebellum at midgestation and in ataxia

A fundamental question in brain development is how neurons make the precise topographic connections necessary for function. The hypothesis that transient expression of calcium (Ca2+) signaling molecules may have a role in this process was tested by studying human cerebella at midgestation. In addition, four adult brains, two controls and two from patients with ataxia, were studied as well. The temporal and spatial distribution of intracellular Ca2+ channel/receptors, inositol trisphosphate receptor type 1 (IP3R1) and ryanodine receptor (RyR) and three Ca2+ binding proteins were examined with immunocytochemical methods. A positive immune reaction with all markers of Ca2+ signaling was found in the Purkinje cell layer starting from 17 g.w. (gestational weeks), the youngest age studied. The immune reactions were not homogeneous throughout the extent of the Purkinje cell layer, but instead displayed a 'patchy' appearance in all intrauterine stages. In the adult cerebellum the expression of Ca2+ signaling molecules was homogenous. In the two cerebella obtained from patients suffering from ataxia, a several-fold reduction of immunostaining with IP3R1 was found. Our findings suggest that transient and differential mobilization of intracellular Ca2+ in seemingly homogenous neuronal types may play a role in development of highly organized projection maps of the cerebellar cortex. Moreover, lack of IP3R1 in the diseased brains suggests that internal stores of Ca2+ play an important role in normal function of the cerebellum.

Transient c-fos gene expression in cerebellar development and functional stimulation

This study examined the temporal appearance of c-fos expression in rat cerebella from birth to postnatal day 21 (P21) and following systemic kainic acid administration in adults. During development, Fos positive granule cells appeared first at P3 in caudal lobules and extended to all folia by P9. These reactive cells occurred in clusters throughout the granular layer and reached their highest reactivity by P15. In addition, Fos positive basket and stellate cells were seen in the molecular layer at this time. A steep decline in Fos protein labeling of the cerebellum began by P18 and was barely detectable in adulthood. In adult rats, systemic injection of kainic acid induced c-fos expression in granule cells and stellate/basket interneurons within 1 h of treatment. Fos reactive granule cells appeared in clusters with some forming distinct parasagittal bands in caudal folia. One day after unilateral cerebellar lesioning, a limited number of reactive cells were found on the lesion margins. A combination of lesioning and systemic kainic acid produced a strong, c-fos expression throughout the ipsilateral granular layer as well as in Purkinje cell nuclei. Contralateral to the lesion, the pattern of granule cell reactivity appeared the same but slightly stronger than those with kainate alone. We conclude that c-fos gene expression occurs transiently in granule cells during postnatal development and can be rapidly re-induced in the adult following systemic injection of glutamate agonists. The c-fos expression patterns suggest that subpopulations of granule cells are clustered and related to the parasagittal compartments of Purkinje cells.

Motilin increases food intake in mice

The effect of motilin on food intake was investigated in nonfood-deprived mice. A significant increase in food intake was observed 1 h after ICV administration of motilin (3 nmol/mouse) and continued for 2 h. This effect was attenuated markedly by the motilin receptor antagonist GM-109 (0.3-3 nmol/mouse) in a dose-related manner. GM-109 alone had no effect on food intake. These results indicate that motilin receptors are present in the brain and may have a role in the regulation of food intake.

Differential staining of two subpopulations of Purkinje neurons in rat cerebellum with acid dyes

We present a new method that stains differently two subpopulations of Purkinje cells in the adult rat. Deparaffinized sections of cerebella, fixed by perfusion with buffered glutaraldehyde or Bouin's fluid were stained with 0.5% light green in 50% ethanol (10-30 min). The excess dye was removed with saturated aqueous picric acid (10-30 min). At this point some Purkinje cells appeared as lightly stained neurons, while others were strongly stained. Slides were immersed in 0.5% aqueous acid fuchsin for approximately 1 min until the lightly stained neurons acquired a red color. Following immersion in 1% phosphotungstic acid, slides were rapidly dehydrated in ethanol, passed to xylene and mounted in Canada balsam. Two subpopulations of Purkinje cells differing in their protein content in somata and proximal dendrites stained differentially by this method. They occurred in all coronal and sagittal sections and in patches or stripes. Their relative proportion varied from lobule to lobule. A second staining method used potassium permanganate as the sole staining reagent. The staining reagent can be used on sections previously stained with the acid dyes. Purkinje cells appeared as subsets of brownish to deep brown stained neurons, the latter ones corresponding to green stained cells in the dichromic method. The results obtained indicated that the subpopulations reflect real differences among individual neurons and are not artifacts. The technique holds promise for identifying and localizing sub-sets of Purkinje cells differing in their protein content under normal and experimental conditions and for their further characterization by combined staining and histochemical procedures.

Identification of motilin mRNA in the brain of man and rabbit. Conservation of polymorphism of the motilin gene across species

The data regarding the identity of motilin-like immunoreactivity in the central nervous system are controversial. The aim of the present study was to clarify whether motilin mRNA is present in the brain of rabbit and man. Total RNA, prepared from several regions of the rabbit brain, was subjected to RT-PCR aimed at amplifying a 294 bp cDNA fragment of the rabbit motilin precursor. The amplified product was subcloned and sequenced. The sequence showed 7 differences compared to the one reported for the duodenal precursor (1). However the duodenal precursor from the rabbit used in the present study revealed identical substitutions. One of these, involving amino acid -11 of the signal peptide, was shown to be due to gene polymorphism, as has also been described at this site in man. By radioimmunoassay the highest concentration of motilin (fmol/mg protein) was detected in the hippocampus (4788 +/- 295), the lowest in the telencephalon (2127 +/- 221). Using a similar approach, but starting from commercial human brain mRNA, the sequence of a comparable cDNA fragment of the human brain motilin precursor was obtained. Its sequence was identical with the one published for the human intestinal precursor (41). Our study demonstrates that motilin mRNA is present in the brain of man and rabbit. Together with our recent findings of central motilin receptors, they suggest a central role for motilin.

The compartmentalization of the cerebellum

The concept of developmental compartments originated in studies of Drosophila embryogenesis. This review examines the hypothesis that the modular structure of the vertebrate cerebellum is strongly analogous to this earlier scheme. The pattern of cerebellar development, the adult circuitry, a variety of molecular markers expressed in specific subdivisions, and the phenotypes of several neurological mutations all provide abundant evidence that the vertebrate cerebellum is organized into modules. We present the case that, as a group, these markers reveal distinct boundaries that partition the cerebellum into true developmental compartments. Although this reductionist viewpoint advances our understanding of cerebellar organization, the relationship between these compartments and the functional behavior of the cerebellum remains a mystery.

Motilin and clinical application

Motilin is a regulatory polypeptide of 22 amino acid residues and orginates in motilin cells scattered in the duodenal epithelium of most mammals and chickens. Motilin is released into the general circulation at about 100-min intervals during the interdigestive state and is the most important factor in controlling the interdigestive migrating contractions. Recent studies have revealed that motilin stimulates endogenous release of the endocrine pancreas. Clinical application of motilin as a prokinetic has become possible since erythromycin and its derivatives were proved to be nonpeptide motilin agonists.

Expression pattern of integrin beta 1 subunit in Purkinje cells of rat and cerebellar mutant mice

We found that integrin beta 1 subunit (INT beta 1)-immunoreactive Purkinje cells first appeared caudally at postnatal day (PD) 6 of rat and most Purkinje cells gradually became positive by PD 12. The expression of INT beta 1 was then suppressed in some of these cells, so that the positive Purkinje cells in the adult were organized into parasagittal bands interposed by negative cells throughout the vermis and hemispheres. When Purkinje cells were deprived of their climbing fiber innervation by inferior cerebellar pedunculotomy or by transplantation of cerebellar anlagen into the anterior eye chamber, the subsequent patterning of INT beta 1-positive Purkinje cells was not changed. In both reeler and weaver mice, the INT beta 1-positive parasagittal bands were observed, however, the Purkinje cells in the staggerer mice did not express INT beta 1 at any stage. These data suggest that the expression of INT beta 1 in Purkinje cells is genetically programmed in the developing cerebellum, and that the afferent synaptic inputs by climbing and parallel fibers are not prerequisites for INT beta 1 expression in Purkinje cells. Therefore, the unique distribution patterns of INT beta 1-positive Purkinje cells provides a new marker for postnatal development of rodent cerebella.

Ontogeny of GABA-immunoreactive cells in the primate cerebellar cortex: comparison with somatostatin-immunoreactivity

The distribution and ontogeny of GABA-immunoreactive cells were studied and compared with that of somatostatin-immunoreactivity in the primate cerebellar cortex. At embryonic day 80, we observed neither GABA-nor somatostatin-immunoreactive cells in the cerebellum. At embryonic day 110, a small number of GABA-immunoreactive cells was detectable in the granular layer only, and these cells seemed to be Golgi cells. At embryonic day 140, although almost all Purkinje cells were somatostatin-immunoreactive, a proportion of these cells was GABA-immunoreactive. At the newborn stage, most of the Purkinje cells were GABA-immunoreactive and almost all of them were also somatostatin-immunoreactive. During the postnatal stages, the number of somatostatin-immunoreactive cells decreased until postnatal day 60. At the adult stage, a large number of Purkinje cell bodies was faintly GABA-immunoreactive and a proportion of Purkinje cell dendrites was GABA-immunoreactive. In the aged animals (28 and 31 years old), a small number of Purkinje cell dendrites was GABA-immunoreactive. These findings suggest that a transition of phenotype from somatostatin to GABA occurred in Purkinje cells during development.

Regional variation in expression of calbindin and inositol 1,4,5-trisphosphate receptor type 1 mRNAs in the cerebellum of the staggerer mutant mouse

The Purkinje cells in the staggerer mutant mouse have various cellular abnormalities, including reduced cell number, ectopia, smaller size and absence of dendritic spines. It is also know that some of these abnormalities exhibit regional variations in the cerebellum. In this paper we have investigated expression in the staggerer Purkinje cells of the calbindin and inositol 1,4, 5-trisphosphate receptor type 1 mRNAs by in situ hybridization. Although the transcription levels of both mRNAs were significantly reduced compared with the wild-type cells, the reduction among the Purkinje cell populations was not even, varying greatly from region to region. Purkinje cells with different transcription levels were distributed in discrete regions and arranged alternately in the mediolateral direction. Moreover, the cell bodies with higher transcription levels were larger in size and aligned in a monolayer between the granular and molecular layers, whereas those with lower levels were smaller in size, fewer in number and dispersed throughout the granular layer. These findings suggest that there is a distinct mediolateral heterogeneity in the staggerer cerebellum with respect to transcription levels of these Purkinje cell-specific molecules, which might correlate with some cytological phenotypes.

Neuronal migration abnormality in peroxisomal bifunctional enzyme defect

Patterns of brain dysgenesis that resemble those in the Zellweger syndrome were demonstrated in a boy with an isolated defect of the peroxisomal bifunctional enzyme. There was bilateral centrosylvian pachygyria and polymicrogyria, diffuse hemispheric hypomyelination with heterotopic neurons, Purkinje cell heterotopias, and simplified convolutions of the dentate nucleus and inferior olive. This association of Zellweger syndrome-like brain dysgenesis with a defect of a single peroxisomal enzyme provides new opportunities for the study of pathogenetic mechanisms in peroxisomal disorders.

Chemical heterogeneity in adult rat cerebellar Purkinje cells as revealed by zebrin I and low-affinity nerve growth factor receptor immunocytochemical expression following injury

Cerebellar Purkinje cells in rat express low-affinity nerve growth factor receptor during development, but rarely in normal adult animals. However, after either mechanical injury or colchicine treatment during adulthood, these cells re-express low-affinity nerve growth factor receptor-immunoreactive protein. Two Purkinje cell subpopulations were defined in normal adult cerebellum by the presence or the absence of zebrin I antigen. Nevertheless, it remains an open question as to whether low-affinity nerve growth factor receptor-immunoreactive protein can be expressed by all damaged Purkinje cells, independent of their location and their staining with antibodies against intrinsic molecular markers that reveal Purkinje cell heterogeneity, such as zebrin I. In this study, a serial-section immunocytochemical mapping of the expression zebrin I and low-affinity nerve growth factor receptor, using specific monoclonal antibodies, we carried out in colchicine-treated rats. After mechanical damage of the cerebellar cortex, co-localization of these antigens at the cellular level was also analysed in thin adjacent sections, and by using a combined immunocytochemical staining method in individual sections. The findings revealed the existence of three sub-sets of Purkinje cells: (1) two complementary groups distinctly immunoreactive to one antibody, but not to the other and (2) a third group that contained double-labelled cells. In contrast, co-expression of both antigens was never observed following mechanical lesions. The seemingly independent response to mechanical injury of Purkinje cells located in different zebrin-defined compartments, indicates that particular subpopulations of Purkinje cells may respond differentially to traumatic injury.

Anatomical compartments in the white matter of the rabbit flocculus

The white matter of the rabbit flocculus is subdivided into five compartments by narrow sheets of densely staining acetylcholinesterase-positive fibers. The most lateral compartment is continuous with the C2 compartment of the paraflocculus and contains the posterior interposed nucleus. The other four compartments are numbered from lateral to medial as floccular compartments 1, 2, 3, and 4 (FC1-4). FC1-3 continue across the posterolateral fissure into the adjacent folium (folium p) of the ventral paraflocculus. FC4 is present only in the rostral flocculus. In the caudal flocculus FC1 and FC3 abut dorsal to FC2. Fibers of FC1-4 can be traced into the lateral cerebellar nucleus and the floccular peduncle. The presence of acetylcholinesterase in the deep stratum of the molecular layer of the flocculus and ventral paraflocculus distinguishes them from the dorsal paraflocculus. The topographical relations to the flocculus and the floccular peduncle with group y and the cerebellar nuclei are discussed.

A combined retrograde tracer and GABA-immunocytochemical study of the projection from nucleus interpositus posterior to the posterior lobe C2 zone of the cat cerebellum

The extent to which the cells of origin of the cerebellar nucleocortical pathway are immunopositive for gamma-aminobutyric acid (GABA) was investigated in four cats using retrograde labelling of nucleocortical neurons in combination with immunocytochemistry. Neurons were retrogradely labelled by injection of fluorescent (coumarin)-tagged latex microspheres into the c2 zone in the rostral part of the paramedian lobule. The zone was identified electrophysiologically by the characteristics of the climbing fibre responses evoked on the cerebellar surface by percutaneous stimulation applied to the left and right forepaws in pentobarbitone-anaesthetized animals. Sections of the cerebellum containing the retrogradely labelled neurons were processed for GABA immunocytochemistry using a fluorescent (rhodamine)-tagged immunoglobulin. When viewed with epifluorescence microscopy and appropriate filter blocks the retrogradely labelled nucleocortical neurons could be visualized in the same sections as the GABA-immunopositive neurons. Almost all of a total of 254 labelled nucleocortical neurons were located in nucleus interpositus posterior, where a total of 711 GABAergic neurons were also found. None of these cells contained coumarin-tagged beads and displayed immunoreactivity for GABA (i.e. none was double-labelled). When compared by area of their cell body, the nucleocortical and GABA-immunopositive neurons appeared to form two partially overlapping populations. The mean cell area of the nucleocortical neurons was 620 +/- 233 microns2 (SD), whereas the GABA-immunopositive neurons were much smaller, with a mean cell area of 220 +/- 115 microns2. The results suggest that GABA does not play a major role in the nucleocortical pathway to the c2 zone of the rostral paramedian lobule of the cat cerebellum.

Pyridoxal kinase immunoreactivity in rabbit brain

Murine polyclonal antibody against purified bovine brain pyridoxal kinase (EC 2.7.1.35) was generated and showed cross-reactivity with rabbit brain pyridoxal kinase. This antibody was used to immunohistochemically examine the distribution of pyridoxal kinase in the rabbit brain. The cytoplasm of neuronal cells and neuroglial cells in the cerebral cortex, hippocampal region, brain nuclei and cerebellar cortex showed positive staining with various degrees of intensity. The neuronal cells and surrounding fibers in some brain nuclei, such as the area tegmentalis ventralis or the substantia nigra, showed intense staining. The neuronal cells of the hippocampal region showed somewhat weak reactivity, but some with intense reactivity were found sparsely distributed and positive staining fiber networks of a very low density were also observed.

Compartmentation of NADPH-diaphorase activity in the mouse cerebellar cortex

The mammalian cerebellum is built around an array of parasagittal bands of Purkinje cells that can be demonstrated by immunocytochemical staining for the differentiation antigen zebrin II. Climbing and mossy fiber afferents also terminate in bands, and the afferent terminal fields and the Purkinje cell bands are aligned. The convergence of mossy and climbing fiber pathways onto the Purkinje cells, which are the sole output of the cerebellar cortex, is a characteristic feature of cerebellar circuitry. Previous studies showed that when both afferent pathways are activated synchronously there develops a long-term depression of synaptic efficacy at the parallel fiber-Purkinje cell synapse. Two second messenger pathways mediate long-term depression: one involves diacylglycerol and protein kinase C, and the other involves nitric oxide that is generated by a nitric oxide synthase. We have studied the distribution of nitric oxide synthase in the adult mouse cerebellum by using nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry. NADPH-diaphorase activity is found mainly in the granule and basket cells. Within the granular layer NADPH-diaphorase activity is expressed nonuniformly by patches of granular cells and synaptic glomeruli. The patches are seen in all lobules, are reproducible from individual to individual, and are topographically ordered with respect to the Purkinje cell compartments as revealed by using anti-zebrin II immunocytochemistry. These data imply that nitric oxide-dependent, long-term depression may only involve a subset of mossy fiber/granule cell projections, and that one role for nitric oxide may be to refine cerebellar receptive fields.

Antigenic compartmentation in the mouse cerebellar cortex: zebrin and HNK-1 reveal a complex, overlapping molecular topography

Two monoclonal antibodies--anti-zebrin I and anti-HNK-1--have been used to study the compartmentation of the mouse cerebellar cortex. As in other species, the pattern of localization of the Purkinje cell specific antigen zebrin I is confined to a subset of Purkinje cells that are organized into parasagittal bands. The basic pattern consists of two abutting paramedian bands (P1+) and up to three additional vermal bands on either side (P2(+)-P4+). This pattern is altered in the vermal regions of lobules X and VI-VII where all Purkinje cells are immunoreactive. In the hemisphere there are three additional bands present (P5(+)-P7+) plus two shorter bands in the paravermal area (P4b+ and P5a+) that extend from the paramedian lobule through the lobulus simplex. This pattern is very similar, but perhaps not identical, to that previously described for the rat. These results suggest a common mammalian plan for the expression and localization of zebrin I. By using a monoclonal antibody to an epitope associated with HNK-1, we have now identified a novel pattern of compartmentation in mouse cerebellum. The HNK-1 epitope is expressed most notably on Purkinje cells and Golgi cells. The molecular layer immunoreactivity associated with the Purkinje cell dendrites varies in intensity in a systematic and reproducible fashion. This reveals a novel cerebellar compartmentation that is sometimes complementary, sometimes overlapping, to that revealed by anti-zebrin. As a result, it is now possible to subdivide the cerebellar cortex into a still finer mosaic of antigenic patches and bands than was possible by using zebrins alone.

Cholinergic innervation of the human cerebellum

Cholinergic innervation of the human cerebellum was investigated immunocytochemically by using a polyclonal rabbit antiserum against choline acetyltransferase. Immunoreactive structures were found throughout the cerebellar cortex but were localized predominantly in the vermis, flocculus, and tonsilla. These included 1) a population of Golgi cells in the granular layer; 2) a subpopulation of mossy fibers and glomerular rosettes; 3) thin, varicose fibers closely associated with the Purkinje cell layer and the molecular layer; and 4) a relatively dense network of fibers and terminals contributing to the glomerular formations in the granular layer. In the cerebellar nuclei, some cells stained positively for choline acetyltransferase, and a terminal field pattern could be detected with a distinct but sparse network of varicose fibers. Acetylcholine appears to be a primary transmitter in the vestibulocerebellar pathways at several levels, which may account for the potent effects of muscarinic antagonists in diminishing vestibular vertigo in humans.

Cerebellar degeneration in the Niemann-Pick type C mouse

Chronological morphological changes and topographical distribution of degenerating Purkinje cells were studied in the murine model of Niemann-Pick disease type C (NPC mouse). Loss of Purkinje cells can be detected in the anterior vermis as early as 60 days of age, coinciding with early neurological signs, and progressed to total absence in the entire hemisphere and vermis with exception of nodules. Ultrastructurally, concentric lamellar inclusions were detected in the perikarya of degenerating Purkinje cells as well as in the focally enlarged branching points of their dendrites. Calbindin immunocytochemistry demonstrated dendritic pathology characterized by irregular contour of dendritic trees and decreased number of dendritic spines. Ubiquitin immunoreactivity revealed granular reaction products in the perikarya, dendrites and axons of Purkinje cells. Our studies demonstrated unique pathological features of Purkinje cells that involve perikarya, dendrites and axons in the NPC mouse.