Methamphetamine (Meth) at higher (but not lower) concentration increased inwardly rectifying K+ currents in human fetal astrocytes (HFAs). (a) Sample traces of inwardly rectifying K+ currents (IKir) indicate that 100 μM (but not 20 μM) Meth increased IKir in HFAs. (b) The I-V relationships reveal that IKir was significantly increased by 100 μM Meth compared to controls (Control vs. 20 and 100 μM Meth, n = 32/26 vs. 17/12 and 9/7 cells/independent experiments; Two-Way rmANOVA: Treatment effect: F(2,55) = 1.41, p > 0.05; Voltage effect: F(8,440) = 60.91, p < 0.001; interaction: F(16,440) = 2.889, p = 0.0002; with Newman–Keuls post hoc test: *,**p < 0.05 or 0.01).