Synaptic inhibition mediated by GABAB receptors in the neonatal rat spinal cord in vitro.

In the neonatal rat spinal cord in vitro prolonged inhibition of dorsal root to ventral root reflexes was achieved by electrical stimulation of an adjacent ipsilateral dorsal root. This prolonged inhibition lasted in excess of 1 s. An early phase of the prolonged inhibition was reduced by the GABAA receptor antagonist bicuculline methochloride with a concomitant reduction of dorsal root potentials which are an indication of primary afferent depolarisation. A longer latency and duration component of prolonged inhibition could be blocked by the selective GABAB receptor antagonist CGP56999A and therefore appeared to be mediated by baclofen-sensitive GABAB receptors. This GABAB receptor antagonist did not reduce dorsal root potentials suggesting that the component of prolonged inhibition mediated by GABAB receptors did not involve primary afferent depolarisation.