Distribution and structure of synapses on medial vestibular nuclear neurons targeted by cerebellar flocculus purkinje cells and vestibular nerve in mice: Light and electron microscopy studies Journal Article


Author(s): Matsuno, Hitomi; Kudoh, Moeko; Watakabe, Akiya; Yamamori, Tetsuo; Shigemoto, Ryuichi; Nagao, Soichi
Article Title: Distribution and structure of synapses on medial vestibular nuclear neurons targeted by cerebellar flocculus purkinje cells and vestibular nerve in mice: Light and electron microscopy studies
Affiliation IST Austria
Abstract: Adaptations of vestibulo-ocular and optokinetic response eye movements have been studied as an experimental model of cerebellum-dependent motor learning. Several previous physiological and pharmacological studies have consistently suggested that the cerebellar flocculus (FL) Purkinje cells (P-cells) and the medial vestibular nucleus (MVN) neurons targeted by FL (FL-targeted MVN neurons) may respectively maintain the memory traces of short- and long-term adaptation. To study the basic structures of the FL-MVN synapses by light microscopy (LM) and electron microscopy (EM), we injected green florescence protein (GFP)-expressing lentivirus into FL to anterogradely label the FL P-cell axons in C57BL/6J mice. The FL P-cell axonal boutons were distributed in the magnocellular MVN and in the border region of parvocellular MVN and prepositus hypoglossi (PrH). In the magnocellular MVN, the FL-P cell axons mainly terminated on somata and proximal dendrites. On the other hand, in the parvocellular MVN/PrH, the FL P-cell axonal synaptic boutons mainly terminated on the relatively small-diameter (< 1 μm) distal dendrites of MVN neurons, forming symmetrical synapses. The majority of such parvocellular MVN/PrH neurons were determined to be glutamatergic by immunocytochemistry and in-situ hybridization of GFP expressing transgenic mice. To further examine the spatial relationship between the synapses of FL P-cells and those of vestibular nerve on the neurons of the parvocellular MVN/ PrH, we added injections of biotinylated dextran amine into the semicircular canal and anterogradely labeled vestibular nerve axons in some mice. The MVN dendrites receiving the FL P-cell axonal synaptic boutons often closely apposed vestibular nerve synaptic boutons in both LM and EM studies. Such a partial overlap of synaptic boutons of FL P-cell axons with those of vestibular nerve axons in the distal dendrites of MVN neurons suggests that inhibitory synapses of FL P-cells may influence the function of neighboring excitatory synapses of vestibular nerve in the parvocellular MVN/PrH neurons.
Journal Title: PLoS One
Volume: 11
Issue 10
ISSN: 1932-6203
Publisher: Public Library of Science  
Date Published: 2016-10-01
Start Page: Article number: e0164037
Copyright Statement: CC BY 4.0
Sponsor: This work was supported by RIKEN [to SN]; Grant-in-Aid from the Japan Society for the Promotion of Science, https://www.jsps.go.jp/english/e-grants/ [22300112 to SN].
URL:
DOI: 10.1371/journal.pone.0164037
Open access: yes (OA journal)