The effects on synaptic of Lioresal activity in the isolated spinal cord

Abstract
The perfused in vitro frog: spinal cord preparation was used as an experimental model to investigate thie effects of Lioresal and GABA on the spinal cord. Both compounds reduceid depolarizing synaptic potentials and depressed propagated reflex activity recorded from the ventral roots. However, in contrast to GABA, which produced potent effects on rnotoneurons, Lioresal produced only minor alterations of motoneuron excitability and membrane potential and the resporise of motoneurons to glutamate and aspartate, putative excitatory transmitters. Lioresal had effects on presynaptic structures, decreasing the excitability of and hyperpolarizing dorsal root terminals; GABA depolarizedl the same terminals. These data suggest that Lioresal produces most of its actions presynaptically, possibly by blocking impulse conduction in preterminal axons. This mechanism may contribute to the clinical effects OX Lioiresal in patients with spasticity.