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A new substance, quisqualamine, the decarboxylated analogue of quisqualic acid, predictably depressed electrical activity of neurons of the frog and rat spinal cord in vitro and of the mouse spinal cord in vivo. In the in vitro preparations, the action of quisqualamine was associated with a prolonged depolarization of primary afferent terminals which was sensitive to blockade by picrotoxin and bicuculline and which was also depressed by strychnine. This suggests an interaction of quisqualamine with presynaptic receptors for both GABA and 8-alanine. Post-synaptic actions of quisqualamine, which were less marked than those at pre. synaptic sites, also appeared to be predominantly GABA-mimetic in vitro, though a sensitivity to the GABA-antagonist bicuculline could not be demonstrated in vivo.

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