Figure 8.

Whole cell patch clamp recordings indicate that CCL2 treatment in naïve neurons rapidly induced spontaneous activity in vitro. A representative trace (A) shows CCL2-induced changes in membrane potential and spontaneous discharge. The area indicated by the dotted lines in (A) is presented in (B), and shows normal, low-level fluctuations at baseline, while the area indicated by the solid lines is presented in (C) and shows enhanced fluctuations in membrane potential and action potentials after CCL2 administration. Spontaneous activity ceased after a brief washout period. Application of CCL2 at the lower concentrations (5 or 10 pg/ml) resulted in membrane depolarization in 4 of 7 neurons (D, black line), while 3 of 7 neurons showed no change in membrane potential (D, gray line). Yet, the overall mean membrane potential was not significantly changed by CCL2 applied at this concentration (E, left). When tested at the higher concentration (50 pg/ml), 6 of 8 neurons were depolarized during CCL2 administration at this concentration (D, solid and dashed black line) and 5 of 8 neurons showed evoked action potentials (dashed line). Relative to baseline, mean resting membrane potential was significantly lower after administration of the higher concentration (50 pg/ml) of CCL2 (E, right, paired t-test, p<0.05).