Glycine effects on in vitro motor pattern generation in mouse spinal cord.

Bath applications of glycine typically inhibited electromyogram (EMG) activity in the gastrocnemius (G) and tibialis anterior (TA) muscles of neonatal mice, in vitro. Although rhythmic bursting occurred in response to glycine administration, cycle alternation between individual EMG bursts in G and TA muscles was not observed. That strychnine (a glycine 1 receptor antagonist) and cycloleucine (a glycine 2 receptor antagonist) could evoke motor rhythm, when given separately or in combination, confirms that glycine transmission is not required for motor pattern generation in mice. Strychnine application resulted in synchronized EMG bursting in G and TA muscles, suggesting that glycine 1 receptor activation does provide some reciprocal inhibition between the G and TA motor nuclei.