Distribution of Dendrites from Longissimus Lumborum Motoneurons Stained Intracellularly with Biocytin in Adult Cats

Abstract

ABSTRACT. The three-dimensional distribution of dendrites from motoneurons innervating longissimus lumborum (Long Motoneurons) in the L4 spinal segment was examined in the adult cat using intracellular staining techniques. Long Motoneurons were electrophysiologically identified, stained with injection of biocytin and reconstructed from serial histological sections. Somas of Long Motoneurons were mainly located in the lateral-ventral area of the ventral horn. The dendritic distribution followed an orderly pattern in all motoneurons examined. Long Motoneurons showed a multi-directional distribution of dendrites, and the dendritic distribution pattern varied depending on the motoneuron. All studied motoneurons distributed dendrites from the spine into the white matter. The most significant morphological characteristic of the Long Motoneurons was the variation in their dendritic distribution. No relationship was observed between the effects of peripheral afferent inputs from the hindlimb and morphological characteristics of motoneurons.KEY WORDS: biocytin, feline, motoneurons, postsynaptic potentials, trunk muscles.J. Vet. Med. Sci. 72(8): 1093-1097, 2010 The trunk is the main mass of the body in most animals and is located in the center of the body. The center of gravity (COG) is located in the trunk during most types of movement and in most postures. The position of the COG is influenced by movements, and the movements of all body parts are controlled by the activity of trunk muscles. Neuronal control of trunk muscles during locomotion has been investigated [20,23]. The erector spinae control body balance by increasing spinal column stiffness and/or inducing inward movements from the lateral side during locomotion. Macpherson et al. [15,16] reported the activity of neuronal control of trunk muscles in a standing position. Somatosensory information from different body parts is very important for controlling trunk muscle activities. Experiments using intracellular recording techniques demonstrate that the trunk muscle motoneurons have strong effects on muscle and cutaneous afferent inputs from mechanical receptors in different body parts [21,22,24,25].A motoneuron is composed of dendrites, a cell body, and axons. The morphological characteristics of motoneurons are considered to reflect their functional characteristics. Morphological studies are very important for understanding the functional aspects of motoneurons. Previous studies have demonstrated the morphological characteristics of spinal motoneurons innervating the hindlimbs, the tail, and the cervical muscles [8,14,18], and there may be a close relationship between dendritic distribution and the soma location of motoneurons [2,8,9]. Holstege et al. [11] reported that the soma location of motoneurons innervates trunk muscles. However, the morphological characteristics of trunk muscle motoneurons have not been characterized. The purpose of the present study is to demonstrate the morphological characteristics of motoneurons innervating longissimus lumborum (Long...

Effects of Reducing Suppressors of Cytokine Signaling-3 (SOCS3) Expression on Dendritic Outgrowth and Demyelination after Spinal Cord Injury

“…However, the distribution of dendrites from local spinal cord neurons and how to promote the growth of these dendrites after SCI are still unclear. The extension of dendrites in the white matter from spinal cord neurons receives inputs from descending pathways [ 11 ]. The distribution of dendritic trees and the location of soma in certain spinal cord neurons may correlate with their function [ 12 , 13 ].…”