Figure 5.

GABA-evoked Ca²⁺ increases and burst firing. A, Synaptically evoked spike burst in a TRN neuron recorded in whole-cell current clamp (30 mm Cl⁻). Action potentials were blocked by either depolarizing the neuron to −60 mV or following application of TTA-P2 (1 μm). B, Summary data showing that synaptically evoked burst firing recorded in whole-cell current clamp is controlled by resting membrane potential and blocked by TTA-P2 (1 μm) (n = 5; p < 0.001, paired Student's t test). C, A representative experiment showing that brief application of muscimol (500 μm; 100 ms; time of application indicated by the bar) triggered Ca²⁺ increases in the distal dendrite of a TRN neuron recorded whole cell current clamp with a K-based internal solution (30 mm Cl⁻) supplemented with Fluo-4 (125 μm). Ca²⁺ increases were blocked by TTA-P2 (1 μm). TTA-P2 had little effect on muscimol-induced postsynaptic membrane depolarization. Recordings were performed in presence of TTX (0.5 μm). D, Summary plot showing that muscimol-induced Ca²⁺ increases were significantly reduced by bath application of TTA-P2 (1 μm; p < 0.05; n = 5; paired Student's t test). The muscimol-induced postsynaptic membrane depolarization is not significantly reduced by TTA-P2. Error bars indicate SEM.