TRPV1 Inhibits the Ventilatory Response to Hypoxia in Adult Rats, but Not the CO2-Drive to Breathe

Figure 1. Effects of intracerebroventricular (icv) microinjection of vehicle (DMSO), AMG9810 (TRPV1 antagonist—2.85 µg/kg, 1 µL) and AMG7905 (TRPV1 antagonist—28.5 µg/kg, 1 µL) on ventilation (V˙E), tidal volume (VT) and respiratory frequency (fR) of rats during normocapnia and hypercapnia (7% CO2). The arrow indicates the time of the microinjection. The hypercapnia duration is represented by a horizontal line on the graph. Values are expressed as mean ± S.E.M.

Figure 2. Effects of intracerebroventricular (icv) microinjection of vehicle (DMSO), AMG9810 (TRPV1 antagonist—2.85 µg/kg, 1 µL) and AMG7905 (TRPV1 antagonist—28.5 µg/kg, 1 µL) on (A) mean arterial pressure (MAP) and heart rate (HR) and (B) body temperature (Tb) of rats during normocapnia and hypercapnia (7% CO2). The arrow indicates the time of the microinjection. The hypercapnia duration is represented by a horizontal line on the graph. Values are expressed as mean ± S.E.M.

Figure 3. Effects of intracerebroventricular (icv) microinjection of vehicle (DMSO), AMG9810 (TRPV1 antagonist—2.85 µg/kg, 1 µL) and AMG7905 (TRPV1 antagonist—28.5 µg/kg, 1 µL) on ventilation (V˙E), tidal volume (VT) and respiratory frequency (fR) of rats during normoxia and hypoxia (10% O2). The arrow indicates the time of the microinjection. The hypoxia duration is represented by a horizontal line on the graph. Values are expressed as mean ± S.E.M. * Significant differences between AMG9810 with vehicle and AMG7905 groups. +Significant difference between AMG7905 and AMG9810 groups.

Figure 4. Effects of intracerebroventricular (icv) microinjection of vehicle (DMSO), AMG9810 (TRPV1 antagonist—2.85 µg/kg, 1 µL) and AMG7905 (TRPV1 antagonist—28.5 µg/kg, 1 µL) on (A) mean arterial pressure (MAP) and heart rate (HR) and (B) body temperature (Tb) of rats during normoxia and hypoxia (10% O2). The arrow indicates the time of the microinjection. The hypoxia duration is represented by a horizontal line on the graph. Values are expressed as mean ± S.E.M.

Figure 5. Effects of intraperitoneal (ip) injection of vehicle (DMSO) and AMG9810 (TRPV1 antagonist—2.85 µg/kg, 1 mL/kg) on ventilation (V˙E), tidal volume (VT) and respiratory frequency (fR) of rats during normocapnia and hypercapnia (7% CO2). The arrow indicates the time of the microinjection. The hypercapnia duration is represented by a horizontal line on the graph. Values are expressed as mean ± S.E.M.

Figure 6. Effects of intraperitoneal (ip) injection of vehicle (DMSO) and AMG9810 (TRPV1 antagonist—2.85 µg/kg, 1 mL/kg) on (A) mean arterial pressure (MAP) and heart rate (HR) and (B) body temperature (Tb) of rats during normocapnia and hypercapnia (7% CO2). The arrow indicates the time of the microinjection. The hypercapnia duration is represented by a horizontal line on the graph. Values are expressed as mean ± S.E.M.

Figure 7. Effects of intraperitoneal (ip) injection of vehicle (DMSO) and AMG9810 (TRPV1 antagonist—2.85 µg/kg, 1 mL/kg) on ventilation (V˙E), tidal volume (VT) and respiratory frequency (fR) of rats during normoxia and hypoxia (10% O2). The arrow indicates the time of the microinjection. The hypoxia duration is represented by a horizontal line on the graph. Values are expressed as mean ± S.E.M. * Significant difference between vehicle and AMG9810 groups.

Figure 8. Effects of intraperitoneal (ip) injection of vehicle (DMSO) and AMG9810 (TRPV1 antagonist—2.85 µg/kg, 1 mL/kg) on (A) mean arterial pressure (MAP) and heart rate (HR) and (B) body temperature (Tb) of rats during normoxia and hypoxia (10% O2). The arrow indicates the time of the microinjection. The hypoxia duration is represented by a horizontal line on the graph. Values are expressed as mean ± S.E.M. * Significant difference between vehicle and AMG9810 groups.

Figure 9. Relationship between pulmonary ventilation (V˙E; data from Figure 7) and body temperature (Tb; data from Figure 8B) in rats treated with vehicle (DMSO) or AMG9810 (TRPV1 antagonist—2.85 µg/kg, 1 mL/kg). The direction of time is shown with arrows, and the times corresponding to the earliest (5 min) and latest (35 min) hypoxia exposure data points are indicated. Values are expressed as mean ± S.E.M.