Figure 4. Firing in GABAergic pacemaker neurons is altered but not blocked by glutamatergic antagonists.

GABAergic neurons fire bursts of action potentials during XII bursts. Cells were patch clamped in the current clamp configuration with a small amount of current (<30 pA) injected to hold the cell at −65 mV. Inspiratory activity was measured from the hypoglossal rootlets (top two traces). Fewer than half of these cells (n = 8/20) continued to fire in the presence of CNQX and AP-5. In cells that showed continued activity, the synaptic activity to these neurons, as well as voltage gated calcium channels, were blocked by addition of cadmium chloride. Pacemaker activity patterns changed but frequencies between the three groups was not significantly different (Control: 1.7+/−0.4 Hz; CNQX & AP5: 1.7+/−0.5 Hz; CdCl₂: 1.8+/−0.6 Hz).