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Developmental changes in rhythmic spinal neuronal activity in the rat fetus.
Norio Kudo1, Hiroshi Nishimaru, Kiyomi Nakayama
1Department of Physiology, Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan. kudo@md.tsukuba.ac.jp
Progress in Brain Research
|December 5, 2003
Summary
During prenatal development, the rat spinal cord forms a locomotion central pattern generator. Glycine and glutamate receptor activity drives rhythmogenesis, with inhibitory circuits crucial for alternating limb movements.
Area of Science:
- Neuroscience
- Developmental Biology
- Spinal Cord Research
Background:
- Locomotion in mammals is controlled by central pattern generators (CPGs) in the spinal cord.
- The prenatal development of these CPGs involves significant changes in synaptic transmission and circuitry.
- Understanding the precise roles of different neurotransmitters and neuronal circuits during development is critical.
Purpose of the Study:
- To investigate the roles of glycine and glutamate receptor-mediated synaptic transmission in prenatal spinal cord development.
- To elucidate the developmental timeline of inhibitory circuitry formation and its contribution to motor pattern generation.
- To differentiate the mechanisms underlying left/right limb alternation versus flexor/extensor muscle alternation.
Main Methods:
- Analysis of synaptic transmission properties during prenatal development in rat spinal cord models.
- Electrophysiological recordings to assess neuronal activity and rhythmogenesis.
- Pharmacological manipulations to investigate the roles of glycine and glutamate receptors.
Main Results:
- Excitatory synaptic transmission via glycine receptors is initially dominant for rhythmogenesis.
- Glutamate-receptor-mediated transmission becomes dominant later in prenatal development.
- Maturation of inhibitory glycinergic circuitry is essential for alternating left/right limb and flexor/extensor muscle activity.
Conclusions:
- Spinal cord locomotion CPGs develop prenatally, with a shift in dominant neurotransmitter roles.
- Developmental changes in postsynaptic neuron properties likely drive left/right alternation.
- Emergence of inhibitory synaptic functions is necessary for flexor/extensor alternation, highlighting the importance of inhibitory circuit maturation.