5-amino-1-(2,6-dichloro-4-trifluoromethyl-phenyl)-3-[3H3]-methylsulfanyl-1H-pyrazole-4-carbonitrile (CTOM): synthesis and characterization of a novel and selective insect GABA receptor radioligand.

Pyrazole 2a is a novel, potent ligand for insect GABA receptors obtained from housefly head membrane preparations (K(i)=8 nM). It is 500-fold selective against the mammalian receptor (mouse brain preparations). Its specifically tritiated version (2b) was synthesized by reduction of disulfide 10 with NaBH(4) followed by alkylation with [3H(3)]-CH(3)I.