Figure 4. Calcium-activated (TRPM4-like) current.

A, average inward and outward currents (in pA pF⁻¹) measured for 350 s, and B, normalized cell capacitance measured for 200 s after break-in from resting (filled) and activated (24 h 1 μg ml⁻¹ LPS, open) microglial cells with 0.6 μm (circles, n = 7/5, ± s.e.m.), 1.7 μm (triangles, n = 13/10, ± s.e.m.) and 40 μm (squares, n = 19/7, ± s.e.m.) free calcium ([Ca²⁺]_i) in the patch pipette. C, plateau inward currents (in pA pF⁻¹) after 350 s versus log [Ca²⁺]_i of resting (•) and activated (24 h 1 μg ml⁻¹ LPS, ^) microglial cells. The sigmoidal fits of the inward current amplitudes revealed an EC₅₀ of 1.2 μm Ca²⁺ (Hill coefficient =−3.5) for resting and 1.3 μm Ca²⁺ (Hill =−6) for activated microglial cells. D, average current–voltage relationships (I–Vs) of whole-cell currents (in pA pF⁻¹) activated by 1.7 μm internal Ca²⁺ from resting (control, continuous traces, n = 9) and activated (24 h 1 μg ml⁻¹ LPS, dotted traces, n = 9) microglial cells at 100 s and 350 s into the experiment.