Chen_1988_Comp.Biochem.Physiol.C_90_317

1. In the optic ganglion of Loligo pealii, binding sites for [3H]-acetylcholine (KD: 5.2 x 10(-7) M; Bmax: 1.7 x 10(-11) mol/g tissue) and 125I-alpha-bungarotoxin (KD: 3.3 x 10(-9) M; Bmax: 9.7 x 10(-11) mol/g tissue) were observed. 2. Both sites are blocked by nicotinic compounds, but differ significantly in their affinity for individual ligands, with the acetylcholine site preferentially binding agonists, and the toxin site, antagonists. 3. The acetylcholine site is substantially more thermolabile than the toxin site. 4. A partial separation of the two binding activities is accomplished by sucrose density centrifugation. 5. These observations and a comparison with other tissues (Torpedo californica electroplaque; chick optic lobe; rat brain) suggest the presence, in the squid, of more than one kind of neuronal nicotinic receptor.