Synapse elimination in the developing cerebellum

Neural circuits in neonatal animals contain numerous redundant synapses that are functionally immature. During the postnatal period, unnecessary synapses are eliminated while functionally important synapses become stronger and mature. The climbing fiber (CF) to the Purkinje cell (PC) synapse is a representative model for the analysis of postnatal refinement of neuronal circuits in the central nervous system. PCs are initially innervated by multiple CFs with similar strengths around postnatal day 3 (P3). Only a single CF is selectively strengthened during P3–P7 (functional differentiation), and the strengthened CF undergoes translocation from soma to dendrites of PCs from P9 on (dendritic translocation). Following the functional differentiation, supernumerary CF synapses on the soma are eliminated, which proceeds in two distinct phases: the early phase from P7 to around P11 and the late phase from around P12 to P17. Here, we review our current understanding of cellular and molecular mechanisms of CF synapse elimination in the developing cerebellum.     

Cilia in stellate neurons of the rat cerebellum

Summary Cilia in stellate neurons of the normal rat cerebellum are described. 8 cilia were observed in a total of 60 cells studied. An 8+1 pattern was found throughout their length. Furthermore, no arms, spokes or other accessory structures necessary for ciliary motion were seen. These findings make it possible to suggest that these cilia are probably without function and are related to the epithelial origin of these cells.This work was granted by INIC: Centro de Morfologia Experimental (MbP₁).Acknowledgments. The authors thank M.A. Rodrigues, M. M. Pacheco, M. C.Pinho and L. B. Nunes for technical assistance.     

Specialized membrane junctions in the avian cerebellum

Summary Pentalaminar specialized membrane junctions-tight junctions — are described in the granular layer of the pigeon cerebellum. The presence of these axo-dendritique and dendrosomatic contacts suggest the existence of electrotonic coupling in the pigeon cerebellum.This work received financial support from the Instituto de Alta Cultura, Lisbon, Project No. PMC5-I.Acknowledgements. I am greatly indebted to Prof.E. G. Gray and Prof.A. Sousa Pinto for helpful advice and criticism. The technical assistance of Mrs.M. M. Pacheco, M. G. Rodrigues, M. L. Brito and Mr.Bessa Nunes is gratefully acknowledged.     

Neuron in the gracile nucleus with myelinated axon hillock

Zusammenfassung Die Ultrastruktur des unmyelinisierten Initialsegments des Ursprungskegels von Achsenzylindern ist bekannt. Im Gegensatz dazu wurde im Nucleus gracilis ein kleines Neuron gefunden, dessen Achsenzylinder kein unmyelinisiertes Initialsegment aufweist: die Myelinscheide beginnt schon auf dem Ursprungskegel und es wird auf die neurophysiologischen Gesichtspunkte, die sich aus diesen Fakten ergeben, hingewiesen.     

The role of the cerebellum in blood pressure regulation

Résumé La stimulation du cervelet du lapin produit seulement des réactions hypertensives. Après la cérebellectomie, la stimulation périphérique provoque — au lieu d'une élévation — une chute de la pression sanguine. Les ondes de Meyer s'intensifient après l'extirpation du vermis et disparaissent après la cérébellectomie totale.     

Dopamine in the visual cortex of the cat

The endogenous content of noradrenaline (NA) and dopamine (DA) was determined by radioenzymatic assays in three different areas of the occipital (visual) cortex, in normal cats as well as in DA-deafferented animals. The use of HPLC methodology enabled us to detect and measure in addition two metabolites of DA: 3, 4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), thus confirming the existence of a DA innervation in this cortical region.     

Binaural interaction in the medulla of the cat

Résumé L'étude de l'orientation latérale dans l'audition binaurale a déjà montré une interaction binaurale dans les réponses électrophysiologiques de l'écorce cérébrale et des tubercules quadrijumeaux inférieurs. Nous avons cherché le niveau le plus bas d'une telle interaction. S'il existe une interaction binaurale aux tubercules acoustiques, elle doit être très faible. Par contre, nous avons trouvé une interaction réelle dans le corps trapezoïde, l'olive supérieure et le lemniscus latéral. Une base anatomique de l'interaction binaurale a été découverte récemment au noyau médial de l'olive supérieure où se trouve une convergence des fibres des deux noyaux cochléaires.

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This research was aided by a grant from the National Science Foundation.     

Immunohistological investigations of N-Acetylserotonin in the rat cerebellum after parachlorophenylalanine treatment

Summary The amount of N-acetylserotonin (NAS) in the granule layer of the rat cerebellum was investigated using immunohistologic double antibody technique. After 5 days of treatment with parachlorophenylalanine (PCPA) an increase of NAS was observed. The possibility of a differential effect of PCPA on serotonin synthesis in the neurons and the nerve terminals is discussed.     

Monoamine pathways to the cerebellum and cerebral cortex

Zusammenfassung In kombinierter histochemischer und biochemischer Untersuchung werden Dopamin-, Noradrenalin-und 5-Hydroxytryptamin-Neurone nach Entfernung von Cortex cerebri und Cerebellum studiert. Es ergibt sich, dass die Noradrenalin-Nerventerminale, welche Cortex cerebri und Cerebellum innervieren, vermutlich von feinen Axonen her stammen, deren Zellkörper mindestens zum Teil in der Formatio reticularis der Medulla oblongata gelegen sind. Die Noradrenalin-und 5-Hydroxytryptamin-Axone, die nach dem Cortex cerebri ziehen, passieren vermutlich zur Hauptsache das Cingulum.     

Immunohistological investigation of N-acetylserotonin in the rat cerebellum after parachlorophenylalanine treatment.

The amount of N-acetylserotonin (NAS) in the granule layer of the rat cerebellum was investigated using immunolohistologic double antibody technique. After 5 days of treatment with parachlorophenylalanine (PCPA) an increase of NAS was observed. The possibility of a differential effect of PCPA on serotonin synthesis in the neurons and the nerve terminals is discussed.     

An electromyographic analysis of stepping in the cat

Zusammenfassung Eine elektromyographische Untersuchung über die Aktivitätsmuster verschiedener Extensormuskeln am Hinterbein einer frei laufenden Katze ist mit Korrelation zu den Bewegungsphasen der Extremität ausgeführt worden.     

Depletion of cerebral monoamines byp-chlorophenylalanine in the cat

Zusammenfassung p-Chlorphenylalanin, ein Inhibitor der Serotoninbiosynthese, senkte bei Katzen den Serotoningehalt des Gehirns nicht selektiv. Es wurde gleichzeitig eine signifikante und langanhaltende Erniedrigung des Noradrenalin- und Dopamingehalts gefunden.     

Histamine receptors in the cat mesenteric circulation

Summary The distribution of histamine receptors was studied in the isolated perfused vascular bed of the cat terminal ileum. The results indicated that the depressor effect of histamine is mediated through the stimulation of metiamidesensitive H₂-receptors, while the pressor effect of the amine is mediated by the stimulation of mepyramine-sensitive H₁-receptors.The authors are indebted to Dr.W. A. M. Duncan, Research Institute, Smith Kline and French Laboratories, Welwyn Garden City, Hertfordshire, England, for his generous gift of metiamide. This work is supported in part by Eczacibasi Research Found. Levent, Istanbul, Turkey.