Fig. 6.

Furosemide effects on muscimol inhibition of VTA GABA neurons. VTA GABA neurons in GAD GFP mice were visualized with fluorescent optics and recorded in cell-attached mode in voltage clamp. A (a, b) These are representative 5-s traces of GABA neuron spike activity recorded before and after muscimol; (c) this ratemeter shows the firing rate of this neuron (traces in a, b recorded at times indicated on graph), which was approximately 10 Hz, before and after application of 0.01–10.0 µM muscimol, which markedly inhibited the firing rate of this VTA GABA neuron. B (a, b) These are representative 5-s traces of the spike activity of another VTA GABA neuron spike activity recorded before and after muscimol in the presence of 100 µM furosemide; (c) this ratemeter shows the firing rate of this neuron (traces in a, b recorded at times indicated on graph), which was approximately 8 Hz, before and after application of 0.01–10.0 µM muscimol. Only 10 µM muscimol inhibited the firing rate of this neuron in the presence of furosemide. C Comparison of muscimol (0.01–10.0 µM) effects on VTA GABA neuron firing rate for control and furosemide treatment conditions. Muscimol significantly inhibited the firing rate of VTA GABA neurons, which was significantly reduced by furosemide. D Whereas in control conditions 100 % of VTA GABA neurons were inhibited in response to muscimol (0.1 µM), furosemide treatment produced muscimol-induced excitation in a significant population of cells. A higher dose of muscimol (1 µM) produced similar results (data not shown)