Caffeine modulates potassium currents in Drosophila neurons

We investigated the effects of caffeine on the delayed-rectifier potassium current (IKDR) which is important in repolarizing the membrane potential, and the transient A-type potassium current (IKA) which regulates neuronal firing threshold and the rate of repetitive action potentials. The whole-cell patch-clamp technique was used to measure the currents from cultured Drosophila neurons derived from embryonic neuroblasts. The currents were measured from neurons before and after the application of 1 mM caffeine to the external saline of the same neuron. IKDR measured in the caffeine-containing solution (470 ± 36 pA, n = 18), was smaller than that measured in the control 6K/0Ca Tris solution (745 ± 51 pA, n = 18). IKA measured in the caffeine-containing solution (17 ± 2 pA, n = 16) was smaller than that measured in the control 6K/0Ca Tris solution (35 ± 4 pA, n = 16).These results indicate that caffeine reduces IKDR and IKA amplitudes and possibly leads to increased action potential frequency and enhanced neuronal excitability.