Figure 5. Effects of TRIP8bnano on voltage-dependent activation of If and spontaneous rate in rabbit sinoatrial node (SAN) myocytes.
(A) Representative whole-cell If currents recorded, at the indicated voltages, in the control solution and in the presence of 10 μM TRIP8bnano, without (top) and with 1 μM cAMP in the pipette (bottom). (B) Mean If activation curves were measured using a two-step protocol (see Materials and methods) in control (filled circles) or in the presence of: 1 µM cAMP (open circles); 10 µM TRIP8bnano (filled squares); 1 µM cAMP +10 µM TRIP8bnano (open squares). Ligands were added in the patch pipette. Half activation potential (V1/2) of If activation curves measured in control = −64.1 ± 0.4 mV or in the presence of: 1 µM cAMP = −59.9 ± 0.4 mV; 10 µM TRIP8bnano = −67.7 ± 0.4 mV; 1 µM cAMP +10 µM TRIP8bnano = −67.6 ± 0.7 mV. Data are presented as mean ± SEM. Number of cells (N) was ≥15. V1/2 values are significantly different between each other’s whit the exception of V1/2 obtained in the presence TRIP8bnano and cAMP +TRIP8 bnano. Statistical analysis performed with two-way ANOVA, followed by post-hoc Bonferroni test (*p<0.05) (C) (Left) Representative recordings of single SAN cell spontaneous activity in control and in the presence of 10 µM TRIP8bnano. (Right) Mean spontaneous rate (Hz) recorded in control solution = 3.65 ± 0.29 Hz and in the presence of 10 µM TRIP8bnano added to the pipette = 2.69 ± 0.27 Hz. Data are presented as mean ± SEM. Number of cells (N) was ≥7. Statistical analysis performed with t test (*p<0.05).