Figure 5.

The kinetics of acidic transients and epileptiform activity differ between seizure models. (A) The membrane potential (upper trace) of a hippocampal CA1 pyramidal neuron during a 0 Mg²⁺ induced seizure episode (seizure duration of 21 s, indicated by the gray bar). The membrane potential reaches its maximum (red dashed line) midway through the seizure. Simultaneous recording of a neighboring pyramidal neuron's intracellular pH (lower trace) reveals that this does not reach its minimum (red dashed line) until 35 s after the seizure terminates and recovers (green dashed line) by approximately 160 s following the end of the seizure. (B) The membrane potential (upper trace) of a CA1 pyramidal neuron during a 0 Cl⁻ induced seizure episode (seizure duration of 69 s, indicated by the gray bar). Unlike the 0 Mg²⁺ induced seizure, the membrane potential reaches its peak (red dashed line) almost immediately after the seizure begins. Simultaneous recording of a neighboring pyramidal neuron's intracellular pH (lower trace), reveals that the intracellular pH reaches its minimum (red dashed line) 23 s before the seizure ends and returns to baseline (green dashed line) approximately 105 s after the end of the seizure episode. (C) The time to reach maximum membrane depolarization as a percentage of seizure duration was significantly longer for 0 Mg²⁺ as opposed to 0 Cl⁻ induced seizures (^***P < 0.0001, t test). (D) The time to reach maximum intracellular pH shift as a percentage of seizure duration was also significantly longer for 0 Mg²⁺ as opposed to 0 Cl⁻ induced seizures (^**P = 0.0031, t test). (E) Similarly, the time of pH recovery as a percentage of seizure duration was significantly longer for 0 Mg²⁺ as compared to 0 Cl⁻ induced seizures (^***P < 0.0001, t test).