“… tetracaine also inhibited radioligand binding to these receptors, … 1 values of 5.25 × 10 −4 M and 4.85 × 10 −5 M for the α-receptor and 8.2 × 10 t-5 M … 6.94 × 10 −6 M for the muscarinic receptor; these inhibitions also appeared to be competitive.”