Specific [3H]LY278584 binding to 5-HT3 recognition sites in rat cerebral cortex

Binding of [3H]LY278584 a 1-methyl-indazole-carboxamide, to putative 5-HT3 recognition sites in membranes isolated from cerebral cortex of rat brain, is examined. Specific binding of [3H]LY278584 accounts for 83-93% of total binding. The unlabelled LY278584 has 500 times greater affinity for [3H]LY278584 recognition sites than its 2-methyl analogue (LY278989), and their potencies parallel their antagonism of the peripheral 5-HT3 receptors. Moreover, the order of potencies of other known antagonists of 5-HT3 receptors supports the conclusion that [3H]LY278584 binds to putative 5-HT3 receptors in cortical membranes.