Competitive chrodrimanin B interactions with rat brain GABA receptors revealed by radioligand binding assays.

Meroterpenoid compounds chrodrimanins produced by Talaromyces sp. YO-2 have been shown to act as competitive antagonists of silkworm larval GABA receptors using electrophysiology, yet no further evidence has been provided to support such an action. We have investigated the actions of chrodrimanin B on rat brain GABA receptors by binding assays with non-competitive ligand of GABA receptors [H]EBOB and competitive ligands [H]gabazine and [H]muscimol. Chrodrimanin B did not significantly affect the binding of [H]EBOB while reducing the binding of [H]gabazine and [H]muscimol to the rat membrane preparations. Chrodrimanin B increased the dissociation constant K of [H]gabazine and [H]muscimol without significantly affecting the maximum binding, pointing to competitive interactions of chrodrimanin B with rat GABA receptors in support of our previous observation that the compound acts as a competitive antagonist on the silkworm larval GABA receptor.