Spinovestibular projections in the rat, with particular reference to projections from the central cervical nucleus to the lateral vestibular nucleus

Abstract

Projections from the spinal cord to the vestibular nuclei were examined following injections of Phaseolus vulgaris-leucoagglutinin, cholera toxin subunit B, or biotinylated dextran at various levels of the spinal cord in the rat. Labeled terminals were abundant after injections of the tracers into the C2 and C3 segments containing the central cervical nucleus. Labeled terminals were seen in the descending vestibular nucleus and the parvocellular, magnocellular, and caudal parts of the medial vestibular nucleus throughout its rostrocaudal extent. Labeled terminals were most numerous in the lateral vestibular nucleus throughout its rostrocaudal extent. The projections from the central cervical nucleus to the vestibular nuclei were exclusively contralateral to the cells of origin because the axons of the central cervical nucleus neurons cross in the spinal cord. Following tracer injections in the cervical enlargement, many labeled terminals were seen in the magnocellular part of the medial vestibular nucleus, but a few were seen in the lateral and the descending vestibular nucleus. Injections into more caudal segments resulted in sporadic terminal labeling in the magnocellular part of the medial vestibular nucleus, the descending vestibular nucleus, and the caudal part of the lateral vestibular nucleus. The results indicate that primary neck afferent input relayed at the central cervical nucleus is mediated directly to the contralateral vestibular nuclei. It is suggested that this projection serves as an important linkage from the upper cervical segments to the lateral vestibulospinal tract in the tonic neck reflex.

Organisation of reciprocal connections between trigeminal and vestibular nuclei in the rat

“…Retrograde labelling studies showed that spinovestibular projections to MVN and IVN originate predominantly from the central cervical nucleus, at level C1-C3, in rats (Bankoul and Neuhuber, 1992). Recently, an abundant projection from C2-C3 levels to LVN was also shown (Matsushita et al, 1995). The present results establish that sensory information reaching the VN originates not only from hindlimbs, forelimbs, and neck, but also by the way of the trigeminal complex, from the face.…”

“…Recent investigations show that vestibulospinal neurones are of small size (Matsushita et al, 1995). Some of these neurones project to the central cervical nucleus (Donevan et al, 1990) and are located in the vestibular region receiving projection from the central cervical nucleus (Matsushita et al, 1995). Therefore, this similar spatial overlap supports the existence of functional reciprocal trigemino-vestibulo-trigeminal and spino-vestibulo-spinal loops which may be primarily concerned with the integration of face and neck functions.…”

“…A similar relationship between vestibulospinal and spinovestibular connections exists. Recent investigations show that vestibulospinal neurones are of small size (Matsushita et al, 1995). Some of these neurones project to the central cervical nucleus (Donevan et al, 1990) and are located in the vestibular region receiving projection from the central cervical nucleus (Matsushita et al, 1995).…”

“…Therefore, the vestibulotrigeminal neurones belong to a population different from that receiving trigeminal afferents. Small vestibular cells are known to project into the inferior olive (Nelson and Mugnaini, 1989) and to the cervical spinal cord (Matsushita et al,1995). Whether the projections from the VN to the trigeminal nuclei are collaterals of the vestibuloolivary and/or vestibulospinal fibres needs further investigation.…”

Cytoarchitecture of the Spinal Cord

“…Vestibulospinal neurons project to the contralateral CeCv (Carleton and Carpenter, 1983;Donevan et al, 1990), this connection serves for the tonic neck (cervicovestibulospinal) reflex (Matsushita et al, 1995). Projections from upper cervical segments to lateral, medial and descending vestibular nuclei also originate from the CeCv (Carleton and Carpenter, 1983;Bankoul and Neuhuber 1992;Matsushita et al, 1995;Xiong and Matsushita, 2001). Projections from upper cervical segments to lateral, medial and descending vestibular nuclei also originate from the CeCv (Carleton and Carpenter, 1983;Bankoul and Neuhuber 1992;Matsushita et al, 1995;Xiong and Matsushita, 2001).…”