Beschreibung:
<jats:title>SUMMARY</jats:title><jats:p>As we have recently shown that GABA should be considered a putative neurotransmitter in<jats:italic>Schistosoma mansoni</jats:italic>, the present work aimed to search for GABA<jats:sub>A</jats:sub>receptors in adult worms using [<jats:sup>3</jats:sup>H]-flunitrazepam to label the allosteric benzodiazepine binding site which is classically present on GABA<jats:sub>A</jats:sub>receptor complexes. We detected a large population (<jats:italic>B</jats:italic><jats:sub>max</jats:sub>=8·25±1·1 pmol . mg protein<jats:sup>−1</jats:sup>) of high affinity (<jats:italic>K</jats:italic><jats:sub>d</jats:sub>=33·6±1·5 n<jats:sc>m</jats:sc>) binding sites for flunitrazepam. These sites harboured a singular pharmacological modulation that does not fit well with a mammalian central benzodiazepine receptor, mainly due to a very high affinity for Ro5-4864 and a very low affinity for clonazepam. We also detected a second population of benzodiazepine binding sites labelled with high affinity (IC<jats:sub>50</jats:sub>=85 n<jats:sc>m</jats:sc>) by [<jats:sup>3</jats:sup>H]-PK11195, a selective ligand of the mammalian peripheral benzodiazepine receptor. In conclusion, this work describes the pharmacological properties of a large population of central-like benzodiazepine receptors supporting their study as putative new targets for the development of anti-parasitic agents. We also describe, for the first time, the presence of peripheral benzodiazepine receptors in this parasite.</jats:p>