Functional knockout of the TRPV1 channel has no effect on the exercise pressor reflex in rats

Figure 1.. In vivo and in vitro effects of capsaicin A, summary in vivo data for the peak pressor responses to intra-carotid injection of capsaicin (0.5 μg in 250 μl) in 16 TRPV1+/+ rats, 15 TRPV1+/− rats and 15 TRPV1−/− rats. Filled circles represent data from males and open circles represent data from females. # signifies that Δ peak mean arterial pressure (MAP) value was significantly greater than its corresponding baseline value (P < 0.0001), which is shown below each vertical bar. Values in parentheses are standard deviations. Baseline values were not significantly different from each other (P > 0.116). Horizontal lines connect means that are significantly different from each other (***P < 0.001). B, summary data for in vitro currents densities evoked by capsaicin (10 μM) in 21 DRG neurons isolated from TRPV1+/+ rats, 16 DRG neurons taken from TRPV1+/− rats and 27 DRG neurons taken from TRPV1−/− rats. C, examples of individual currents evoked by capsaicin (10 μM) and/or ATP (10 μM) applied at the horizontal bar. a, recording from a neuron isolated from a TRPV1+/+ rat. b, recording from a neuron isolated from a TRPV1+/− rat. c, recording from a neuron isolated from a TRPV1−/− rat. d,…

Figure 2.. Summary data for the in vivo responses to static contraction in TRPV1+/+, TRPV1+/− and TRPV1−/− rats A and B, there was no significant difference between the peak pressor responses to static contraction (A) and time courses of the average changes in mean arterial pressure (MAP) during static contraction (B) among the three groups of rats. C–F, likewise, there were no significant differences among the three groups of rats for blood pressure indices (BPI) (C), peak heart rates (HR) (D), peak tensions developed by the statically contracting triceps surae muscles (E) and tension time indices (TTI) developed by the contracting muscles (F). Baseline mean values and standard deviation (parentheses) for MAP and HR are shown below the open columns. # signifies that values are significantly different from their corresponding baseline values (P < 0.001). Filled circles represent values obtained from males and open circles represent values obtained from females. There were no significant differences between baseline values for either MAP or HR.

Figure 3.. Individual examples of the pressor responses to static contraction in TRPV1+/+, TRPV1+/− and TRPV1−/− rats Traces on the left show the pressor responses to contraction evoked by stimulating the tibial nerve at 40 Hz, 0.01 ms and 1.5 times motor threshold. Traces in the middle show that lack of a pressor response to stimulating (40 Hz, 0.01 ms and 1.5 times motor threshold) the tibial nerve when the rats were subjected to neuromuscular blockade with pancuronium. Traces on the right show the pressor responses to stimulating the tibial nerve at 40 Hz, 0.5 ms and 70 times motor threshold. This was done to show that the preparation could still generate a pressor response after it was subjected to neuromuscular blockade. Arrows signify the onset of electrical stimulation. Abbreviations: BP, blood pressure; T, tension.

Figure 4.. Summary data for the in vivo responses to tendon stretch in TRPV1+/+, TRPV1+/− and TRPV1−/− rats A–E, there were no significant differences among the three groups of rats for peak mean arterial pressure (MAP) (A), blood pressure indices (BPI) (B), peak tension (C), tension time indices (TTI) and peak heart rates (HR) (D). Baseline mean values and standard deviation (parentheses) for MAP, HR and tension are shown below the open columns. Filled circles represent values obtained from males and open circles represent values obtained from females. # signifies that values are significantly different from their corresponding baseline values (P < 0.005). There were no significant differences between baseline values for either MAP or HR.

Figure 5.. Summary data for in vivo responses to static contraction in TRPV1+/+ and TRPV1−/− rats with or without occluded femoral artery and vein Baseline values (standard deviation) for MAP, tension and HR are shown inside the columns. Note that the pressor responses to contraction integrated over the 30 s contraction period (i.e. BPI) were equally exaggerated in the TRPV1+/+ and the TRPV1−/− rats. Dashed lines connect the responses of individual rats with or without circulatory occlusion. Filled circles represent values obtained from males and open circles represent values obtained from females. There were no significant differences between baseline values for either MAP or HR. Horizontal lines connect mean values that are significantly different from each other (*P < 0.04).

Figure 6.. Acid-sensing ion channel 1 (ASIC1) and endoperoxide receptor 4 (EP4) antibody expression in TRPV1+/+, TRPV1+/− and TRPV1−/− rats A and B, representative digitally generated blot and quantification of EP4 (A) and ASIC1 (B) in dorsal root ganglion (DRG) tissue isolated from the three groups of rats. For EP4 blots, the bands are shown at 53 kDa. For ASIC1 the bands shown at 64 and 89 kDa represent the non-glycosylated and glycosylated forms of ASIC1, respectively. There is no significant change in the expression of EP4 (P = 0.323) and ASIC1 (P = 0.387) between the three groups.