Abstract
Limb movements during walking in mammals are highly coordinated. The basic spatial and temporal activity patterns of each muscle during such movements are generated in a neuronal circuit in the spinal cord. In this circuit also called the central pattern generator (CPG), synaptic inhibition mediated by inhibitory neurons is considered to be an important element. In vitro isolated spinal cord preparations from neonatal rats and mice have been widely used to study the neuronal mechanism underlying locomotion in mammals. Utilizing this preparation, we have previously shown that GABA and glycine, two major neurotransmitters in the spinal cord, each play important roles in the coordination of the left and right limb activity and its maturation in the prenatal period. Recent studies utilizing genetically engineered mice have facilitated the investigation of the activity and roles of identified interneurons during locomotion. We have recently recorded the activity of Renshaw cells, a population of inhibitory neurons that form recurrent inhibitory connections to motor neurons in isolated spinal cord preparations taken from GAD67EGFP-knock-in mouse neonates. Their synaptic inputs and firing patterns during locomotor-like motor activity suggested that Renshaw cells play a role in regulating the firing of motor neurons during locomotion in rodents. Furthermore, these recordings revealed that Renshaw cells are modulated by the CPG while their firing is not essential for the generation of locomotor activity. [J Physiol Sci. 2007;57 Suppl:S23]
