Figure 4.

β₂AR desensitization also attenuates photorelaxation in mouse trachea. (A) Muscle force in wire myography demonstrating decreased blue light photorelaxation in tracheal rings pretreated with overnight Iso compared with control rings without overnight Iso (22 ± 3.2% vs. 41 ± 3.1% relaxation of initial acetylcholine-induced contraction). **P < 0.0005. n = 9–10. (B) Representative muscle force tracing of tracheal rings with (gray) and without overnight Iso upon blue light treatment (arrowhead) (black). (C) Muscle force in wire myography demonstrating decreased acute Iso-mediated relaxation of an acetylcholine-induced contraction (confirming β₂AR desensitization) in tracheal rings pretreated with overnight Iso compared with rings without overnight Iso (19 ± 4.1% vs. 40 ± 6.1% relaxation of initial contraction). *P < 0.05. n = 9–10. β₂AR = β₂ adrenoceptor; Iso. = isoproterenol.