Glutamic acid is an important excitatory neurotransmitter in the mammalian CNS. It has been established that synaptic transmission is mediated mostly by the ionotropic glutamate receptors AMPA and NMDA, with fast and slow kinetics, respectively. The recent demonstration in hippocampal neurones of a class of glutamate receptors that are activated by kainate and not by AMPA (that is, kainate-selective receptors) opens the possibility that receptors, others than those of the AMPA type, might also be involved in fast neurotransmission. The lack of specific pharmacological tools to dissect out AMPA from kainate receptors has hampered the functional study of kainate receptors. However, the recent finding that a 2,3-benzodiazepine (GYK153655) behaves as a selective antagonist of AMPA receptors allows us to address the question of the role of rapidly inactivating kainate receptors in synaptic transmission.