Experiments with kainate and quisqualate agonists and antagonists in relation to the sub-classification of 'non-NMDA' receptors.

1. The KD values for a range of antagonists including DGG, pCB-PzDA, pBB-PzDA, HDC-QXCA, DNQX and CNQX have been determined using a series of non-NMDA receptor agonists in the isolated spinal cord of the neonatal rat. 2) CNQX and DNQX, and, to a lesser extent, DCH-QXCA, were by far the most potent antagonists, although the degree of selectivity did not vary much throughout the whole range of antagonists used. 3) AMPA and domoate were the most and least sensitive agonists, respectively, to the action of all the antagonists. Ionophoretic experiments in the cat spinal cord in vivo confirmed this order of susceptibility in the case of the antagonists CNQX and pCB-PzDA. 4) Acromelic acid A was a more AMPA-like than domoate-like agonist. 5) The results suggest that two receptors contribute to the responses induced by several of the agonists, and that quisqualate and kainate are less selective agonists at these receptors than are AMPA and domoate, respectively.