Afferent stimulation frequency modulates GABAergic phenomena in the spinal cord: reversal by benzodiazepine antagonists.

Switching from a low (0.5 Hz) to a higher (5 Hz) frequency repetitive stimulation of hindlimb muscle nerve afferents reduced GABA-mediated dorsal root potentials and dorsal root reflexes in the lumbosacral cord of spinal cats. Benzodiazepine receptor antagonists flumazenil and Ro 15-3505 in a very low dose (0.03 mg/kg i.v.) reversed this effect suggesting a stimulation-coupled release of an endogenous benzodiazepine receptor ligand down-regulating GABAA-receptors in the spinal cord.