WAY 100635 has an IC50 of 1.35 nM and is > 100-fold selective for the 5-HT1A site relative to a range of other CNS receptors. The Bmax of [3H]WAY 100635 specific binding is consistently 50-60% greater than that of the agonist radioligand, [3H]8-OH-DPAT. Mn2+, but not guanine nucleotides, inhibits [3H]WAY 100635-specific binding. WAY 100635 has no 5-HT1A receptor agonist actions, but dose-dependently blocks the effects of agonists at both the postsynaptic 5-HT1A receptor in the CA1 region of the hippocampus, and the somatodendritic 5-HT1A receptor locates on dorsal raphe 5-HT neurones. [3H]WAY 100635 has a Kd of approximately 2.5 nM. In the isolated guinea-pig ileum WAY 100635 is a potent and, at high concentrations, an insurmountable antagonist of the 5-HT1A receptor agonist action of 5-carboxamidotryptamine, with an apparent pA2 value (at 0.3 nM) of 9.71.

 

WAY 100635 blocks the inhibitory action of 8-OH-DPAT on dorsal raphe neuronal firing in the anaesthetised rat at doses which has no inhibitory action per se. In behavioural models, WAY 100635 itself induces no overt behavioural changes but potently antagonises the behavioural syndrome induced by 8-OH-DPAT in the rat and guinea-pig (minimum effective dose = 0.003 mg/kg s.c. and ID50 = 0.01 mg/kg s.c., respectively). WAY 100635 also blocks the hypothermia induced by 8-OH-DPAT in the mouse and rat with ID50 values of 0.01 mg/kg s.c.