Figure 10

Effects of alcuronium and gallamine on [³H]ACh binding and ACh-stimulated [³⁵S]GTPγS binding to M ₃ membranes. Effects of the reference allosteric modulators alcuronium (left) and gallamine (right) on kinetics of [³H]ACh binding (top) and ACh-stimulated [³⁵S]GTPγS binding (middle) and concentration response of [³⁵S]GTPγS binding to ACh stimulation (bottom) at M₃ receptors were measured after preincubation of membranes for 60 min with buffer (closed circles) or with 1 μM (open squares) or 10 μM (open triangles) rapacuronium. Then either [³H]ACh (top) or [³⁵S]GTPγS simultaneously with 10 μM ACh (middle and bottom) was added. Incubation was terminated at the times indicated on the x-axis (top and middle) or after 20 min (bottom). Binding is expressed as fmol per μg of protein of specific [³H]ACh (top) or [³⁵S]GTPγS (middle) binding or as fold increase of basal [³⁵S]GTPγS binding (bottom). Data are means ± SE from 3 to 6 independent experiments performed in quadruplicates. Parameters are summarized in Table 7.