Fig. 1.

Spontaneous and evoked epileptiform field potentials in cortical layer V of C1q KO brain slices. (A) Representative responses from P14 wild-type (WT) and C1q knockout (KO) animals to layer VI/white matter stimuli. (A1) Threshold stimulation (1×) evokes a short latency biphasic field potential in WT slice. (A2) Superimposed sweeps from a C1q KO slice show two consecutive responses to identical stimuli (0.2 Hz) that evoke either a short latency field potential, or a long duration, polyphasic all-or-none event. (A3) Epileptiform responses were blocked by increasing stimulus intensity to 2× threshold in slice of A2. Arrow marks time of stimulus. (A4) Additional examples of evoked epileptiform field potentials in slice from different C1q KO mouse. Arrows, action potentials (APs). (B) Spontaneous polyphasic epileptiform event with superimposed AP burst (arrow) from a P30 C1q KO brain slice (upper trace). Lower trace shows spontaneous activity from an age-matched, same-sex WT brain slice recorded simultaneously in the same chamber. (C) Spontaneous epileptiform activity from two electrodes spaced ≈1 mm apart in layer V of C1q KO cortical slice. Diagram shows position of the two recording electrodes. (D) Whole cell voltage clamp recording of bursts of spontaneous EPSCs (upper trace) and IPSCs (lower trace) from a C1q KO layer V pyramidal neuron. When the holding potential (V _h) is −70 mV, a burst of spontaneous inward polyphasic excitatory currents occurs lasting ≈800 ms. When V _h is +20 mV, bursts of spontaneous outward polyphasic inhibitory epileptiform currents are seen in the same neuron. (Scale bar: C, 1 mm.)