Development of the GABAergic network in the mouse spinal cord

Abstract Gamma-amino butyric acid (GABA) is one of the predominant inhibitory neurotransmitters in the spinal cord and negatively regulates neuronal activity. In this chapter, we describe the mature GABAergic system in the spinal cord and its developmental process from the viewpoints of GABAergic neurons and terminals, GABA receptors, GABAergic action, and the GABA removal system based on morphological studies. A ventral-to-dorsal developmental direction exists in the localization of GABAergic neurons and terminals, shift of GABAergic action from excitatory to inhibitory, and formation of the GABA removal system. Changes in GABAergic action and maturation of the GABA removal system parallel the formation of GABAergic synapses. In the ventral horn, the number of the GABAergic synapses peaks on the day of birth, and these synapses gradually shift to glycinergic synapses after birth. In the dorsal horn, GABAergic synapses continue to increase in number until postnatal day 21, and some become GABA and glycine coreleasing synapses during postnatal development.