Central and Peripheral GABA_A Receptor Regulation of the Heart Rate Depends on the Conscious State of the Animal

Figure 2

Effect of diazepam on heart rate in artificially ventilated (1% isoflurane, filled circles; 2.5% isoflurane, open circles; O₂ : N₂O 1 : 1) female guinea pigs (538±27 g). The animals were placed on heated mats and the temperature was monitored and kept constant at 37±1°C throughout the experiment. Electrocardiographic (ECG) recordings were obtained using 2 electrodes placed in the subcutaneous layer of the forelimbs (left and right), and 1 electrode placed in the subcutaneous layer of the left hind limb. ECG recordings were analysed using Chart ADinstrument software and Graphpad Prism 5. A stabilization period of minimum 20 min was performed, followed by NaCl 0.9% i.p. Subsequently the animals were injected intraperitoneally every 25th min with increasing concentrations of diazepam (1, 3 and 10 mg/kg i.p.).