Most knowledge about cys-loop receptors comes from inferences made while studying various members of the family.  Research on the structures of [http://www.proteopedia.org/wiki/index.php/Acetylcholine_binding_protein acetylcholine binding proteins] (AChBP) determined that the binding sites consist of six loops, with the first three forming the principal face and the next three forming the complementary face.  The last loop on the principal face wraps over the ligand in the active receptor.  This site is also abundant in aromatic residues.
Recent literature indicates that the Trp residue on loop B is crucial for both agonist and antagonist binding.  The neurotransmitter is taken into the binding site where it interacts (through hydrogen and cation-π bonding) with the amino acid resides in the aromatic box, located on the principal face of the binding site.  Another essential interaction occurs between the agonist and a tyrosine on loop C. Upon interaction, the loop undergoes a conformational change and rotates down to cap the molecule in the binding site.