Block of GABAb-activated K+ conductance by kainate and quisqualate in rat CA3 hippocampal pyramidal neurones.

Current and voltage-clamp techniques were used to study the effects of kainic (KA) and quisqualic (quis) acids on the slow synaptic inhibition evoked by mossy fibre stimulation in CA3 hippocampal pyramidal neurones in vitro. The K+ conductance underlying the slow synaptic inhibition is coupled to a gamma-aminobutyric acid b (GABAb) receptor by a guanosine-triphosphate (GTP)-binding protein. Both KA and quis reduce (after 7-10 min) the slow inhibitory post-synaptic current (IPSC) without changing the reversal potential. They also reduce the cellular response to exogenously applied (-)baclofen and 5-hydroxytryptamine, which are known to activate a similar K+ conductance. We conclude that KA and quis block the post-synaptic K+ conductance underlying the slow IPSC.