Benzodiazepine receptors in fish brain: [3H]-flunitrazepam binding and modulatory effects of GABA in rainbow trout.

We have identified and partially characterised benzodiazepine binding sites in whole brain membranes of male rainbow trout. In terms of Bmax and KD values trout brain receptors are remarkably similar to those in rat and human brain. The Hill coefficient was 0.98, indicating a single binding site. GABA (10(-4) M) was able to significantly elevate binding of [3H]-FNZ through a change in KD rather than Bmax. This effect was prevented by the GABA receptor antagonist bicuculline methiodide.