The mesencephalic locomotor region in cat: effects of local applications of diazepam and gamma-aminobutyric acid.

In decorticate unanaesthetized cats, displaying sequences of stereotyped locomotor movements in response to electrical stimulation of their footpad, local injections were made into the mesencephalic locomotor region (MLR). Diazepam (at 10 micrograms) and GABA (at 500 micrograms) induced complete suppression for 5-10 min, followed by partial amplitude recovery. It is suggested that: (i) MLR contains both diazepam and GABA receptors, and (ii) diazepam (and GABA) blockade is only short lasting because of a substitution (vicariancy) process through other structures also involved in locomotion.