For GABAergic recordings, the shift in the IPSP amplitude versus membrane potential graphs' x-intercept gave the change in EGABA, while the change in slope provided the relative change in synaptic conductance.
In all recordings, intracellular current steps were applied simultaneously with extracellular stimulation in sequences of 10, from the most negative to the most positive, so that PSP amplitude versus membrane potential graphs could be constructed in Microsoft Excel for each 5 min segment of the recording.
The fast, step-like nature of neocortical AP initiation stands out especially clear in the phase-plot representation, in which the rate of change of the membrane potential is graphed against the instantaneous value of the membrane potential (Figure 1, B1, B2).
The upper graph, labeled "MEMBRANE POTENTIAL", shows the membrane potential, Vm, while the graph in the center, labeled "CURRENTS ACROSS CELL MEMBRANE", shows the sodium (INa), potassium (IK), leak (Ileak), capacitive, and membrane (Im) current densities.
C. Summary graph showing resting membrane potential (RMP) in 4 days sham-exposed mice and 4 days noise-exposed mice (4 days sham-exposed: −64.4 ± 1.2 mV, n = 6; 4 days noise-exposed: −67.7 ± 0.8 mV, n = 14, p = 0.04).
10.7554/eLife.07242.007 Figure 4. Non-tinnitus mice are biophysically distinct from control mice. A. Summary graph of resting membrane potential (RMP) of fusiform cells from control and non-tinnitus mice after blocking spontaneous firing with 0.5 μM TTX (control: −64.2 ± 1.3 mV, n = 14; non-tinnitus: −67.5 ± 0.7 mV, n = 15, p = 0.04).
(D ) Summary graphs of resting membrane potential (left), action potential (AP) threshold (middle), and AP latency (right) measured from MafbCE (dark cyan bar) Mafb CKO (orange bar) and their littermate controls, denoted as CE control (white bar) and CKO control (gray bar) in the graphs, respectively.
There were no differences in maximal leak-dependent respiration and membrane potential (points farthest to the right in the graph) between the two groups of mice.
The voltage region including −69 ± 5 mV (corresponding to the average FSI resting membrane potential ± SD) is highlighted in grey in both graphs.
Block 5: Generates graphs of the temporal evolution of the membrane potential, current densities, and gating variables.
