3-Quinuclidinyl benzylate

FIGURE 4.14 Effects of G-protein on the displacement of the muscarinic antagonist radioligand [sH]-L-quinuclidinyl benzylate by the agonist oxotremorine. Displacement in reconstituted phospholipid vesicles (devoid of G-protein sububits) shown in filled circles. Addition of G-protein (Go 5.9 nmol Py-subunit/3.4 nmol ao-IDP subunit) shifts the displacement curve to the left (higher affinity, see open circles) by a factor of 600. Data redrawn from [14]. 

Fusetani N, Asai N, Matsunaga S, Honda K, Yasumuro K. (1994) Bioactive marine metabolities. 59. CyclosteUettamines A-F, pyridine alkaloids which inhibit binding of methyl quinuclidinyl benzylate (QNB) to muscarinic acetylcholine receptors, from the marine sponge, Stelletta maxima. Tetrahedron Lett 35 3967-3970. 

The binding of quinuclidinyl benzylate ([ H] QNB) to central muscarine receptors is, however, inhibited by Triton X-100, although the effect of the detergent can be prevented to some extent by protection of the receptor with atropine. In the absence of atropine the binding of [ H]-QNB to the membranes is as shown in Fig. 10.17b, a function of surfactant concentration. 

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