ACETYLCHOLINE RECEPTORS IN THE CILIARY GANGLION AND IN THE IRIS MUSCLE OF THE CHICK - SPECIFIC BINDING AND EFFECT ON THE SYNAPTIC TRANSMISSION OF THE NEUROTOXIN FROM NAJA-NAJA-SIAMENSIS

A specific binding of Naja naja siamensis neurotoxin was found both in the iris and in the ciliary ganglion of the chick. Naja‐toxin (125 nm) caused a complete block of the iris muscle contraction induced by carbamyl‐choline. Naja‐toxin had a different effect on the two neuronal populations present in the ganglion: it blocked the synaptically evoked response of the ciliary cells, while the response of the choroid ones was only slightly reduced. The effects were the same in a wide range of concentrations (125 to 2500 nm). The results obtained in the iris show the existence of an acetylcholine receptor population similar to the nicotinic receptor of the skeletal muscle. In the ciliary ganglion the results confirm the existence of different acetylcholine receptors on the two cell types. 1979 British Pharmacological Society