Development of inhibitory synaptic transmission to motoneurons

The inhibitory effects of the neurotransmitters glycine and gamma -aminobut yric acid (GABA) on motoneurons and their role in mediating the timing of m otor output have been understood for some years. Recent work, however, has revealed that these neurotransmitters function very differently in developi ng motor circuits. Most strikingly, both GABA and glycine depolarize neonat al motoneurons, and, in many instances, provide excitatory drive to develop ing motor networks. Additionally, the relative contributions of GABA and gl ycine to inhibitory synaptic transmission in a circuit or, indeed, within t he same synapse, change with postnatal development. Here, we review three f undamental properties of inhibitory neurotransmission that are altered post natally and may be important in shaping the unique behaviors of these synap ses early in development. (C) 2001 Elsevier Science Inc.