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

Figure 3

Effect of GABA 100 μM (left column) or picrotoxin 100 μM (right column) on isolated retrograde perfused female guinea pig hearts. Hearts were excised, mounted in a Langendorff apparatus, instrumented, and perfused with krebs-henseleit solution at a constant pressure of 60 mmHg as previously described [29]. Hearts were left to stabilize for a minimum of 30 min. After 20 min baseline recordings, where flow and heart rate was monitored, the hearts were paced from the right atrium for 2 min at 240 BPM. This protocol was repeated in the presence of GABA 100 μM or picrotoxin 100 μM (𝑛=5; GABA: 677±99 g; Picrotoxin: 672±100 g). GABA 100 μM or picrotoxin 100 μM produced no significant effect on action potential duration (a), flow (b), and heart rate (c).

(a)

(b)

(c)