Interlimb Dynamic after Unilateral Focal Lesion of the Cervical Dorsal Corticospinal Tract with Endothelin-1

Abstract

Handedness is one of the most recognized lateralized behavior in humans. Usually, it is associated with manual superiority regarding performance proficiency. For instance, more than 90% of the human population is considered more skilled with the right hand, which is controlled by the left hemisphere, than with the left. However, during the performance of bimanual tasks, the two hands usually assume asymmetric roles, with one hand acting on objects while the other provides support, stabilizing the object. Traditionally, the role of the two hands is viewed as fixed. However, several studies support an alternate view with flexible assignments for the two hands depending on the task. The supporting role of the hand depends on a closed loop pathway based on proprioceptive inputs from the periphery. The circuit’s efferent arm courses through the dorsal corticospinal tract (dCST) in rodents and terminate on spinal cord interneurons which modulate the excitability of motoneurons in the ventral horn. In the present work, we developed an experimental model of unilateral lesion targeting the cervical dCST with microinjections of the vasoconstrictor endothelin-1 (ET-1) to evaluate the degree of flexibility of forelimb assignment during a food manipulation task. Our results show that just 3 days after unilateral corticospinal tract (CST) injury in the cervical region, rats display severe motor impairment of the ipsilateral forepaw together with a remarkable reversal of motor assignment between the forelimbs.

Inflammatory Response and Secondary White Matter Damage to the Corpus Callosum after Focal Striatal Stroke in Rats

“…In previous studies, we have shown the microinjections of N-Methyl-D-Aspartate (NMDA) into the ventral horn of rat spinal cord caused secondary white matter damage (WM) characterized by axonal degeneration, oligodendrocyte cell death, myelin impairment and intense inflammatory response [ 20 , 21 ]. We also reported that microinjections of endothelin-1 (ET-1) into the rat spinal cord also cause secondary degeneration of white matter tracts [ 23 ]. This phenomenon has also been observed by our group following microinjections of NMDA into the rat striatum [ 16 , 24 , 25 ].…”