Sources of the motor and somatic sensory innervation of the trapezius muscle in the rat

Abstract

ABSTRACT:The study was carried out on nine sexually mature male rats of the Wistar breed weighing approximately 250 g each. Animals were anaesthetized with thiopental sodium injected intraperitoneally (30 mg/kg of body weight). The animals were then injected with Fast Blue tracer into the right trapezius muscle. After a survival period of five weeks the rats were transcardially perfused with buffered paraformaldehyde. The following tissue blocks were collected: spinal cord (cervical and thoracic part) with spinal ganglia and whole brain with medulla oblongata. The tissues collected were cut into 12 μm-thick cryostat sections, which were viewed under a fluorescent microscope equipped with a filter block for FB. FB-positive (FB + ) neurons were counted in every fourth section to avoid double analysis. After injections of the tracer to the right trapezius muscle FB + neurons were found in many nuclei and ganglia. The labelled cells of the medulla oblongata nuclei were found in the bilateral vestibular nuclei including superior (SuVe), lateral (LVe), medial (MVe) and spinal (SpVe) vestibular nuclei and also in the dorsal raphe nucleus (DR) which is a single nucleus, but only in the ipsilateral ambiguous nucleus (Amb). FB + perikarya were also found in the spinal cord, extending between the first cervical segment (C 1 ) and the cranial half of the seventh spinal cervical segment (C 7 ), in an ipsilateral area ventrolateraly with respect to the central canal, within the spinal nucleus of the accessory nerve (SAN). Retrograde labelled sensory neurons were found in the bilateral spinal ganglia (SPG-s), from the second cervical ganglion (C 2 ) to the third thoracic ganglion (Th 3 ).

Immunohistochemical properties of motoneurons supplying the trapezius muscle in the rat

“…As previously described (Sienkiewicz and Dudek 2010) tracer-containing neuronal somata were localised in the ipsilateral nucleus ambiguous. The neurons were multipolar and with relatively large diameter ranging from 40 to 80 μm.…”

“…The animals were housed and treated in accordance with the rules approved by the local Ethics Commission (affiliated to the national ethics Commission for Animal Experimentation, Polish Ministry of Science and Higher Education). The tracing procedure, tissue removal, preparation and cutting, and counting of FB + neurones were described in detail in our previous paper (Sienkiewicz and Dudek 2010). The selected sections comprising FB + neurons mounted on glass slides were processed for double immunofluorescence method.…”

“…It is well known that motoneurons supplying the trapezius muscle in the rat are located in the nucleus ambiguous (Sienkiewicz and Dudek 2010) and in the accessory nucleus of the spinal cord (Kitamura andSakai 1982, Sienkiewicz andDudek 2010). The localisation of motoneurons supplying the trapezius muscle in the rat is well documented but there is no Correspondence to: A. Dudek, e-mail: agnieszka.dudek@uwm.edu.pl information on the immunohistochemical properties of these nerve cell bodies.…”

Transplantation of Xenopus laevis Tissues to Determine the Ability of Motor Neurons to Acquire a Novel Target

“…Such is the case with the trapezius muscle in normal development. The branchial-arch-derived trapezius muscle sits in the trajectory of spinal motor neurons, yet is innervated by motor neuron axons of the spinal accessory nerve or by a branch of the vagus [17], [18], [19]. Thus, it seems plausible that cranial motor neurons and spinal motor neurons rely on unique molecular signatures adapted by their target tissues to prevent cross-innervation at the head-neck boundary.…”

“…Such is the case with the innervation of the trapezius muscle by the spinal accessory nerve rather than spinal motor neurons [17], [18], [19]. Further support for specificity between motor neurons and targets includes studies in some vertebrates showing that spinal motor neurons can reinnervate the correct muscles following nerve transection [20].…”