Fig. 6.

Schematic of a microfluidic device that allows for screening of LGIC concentration response and pharmacological profiles. (a) Channel exits in a custom 12-channel device are shown (numbered above device for clarity; not to scale). Even-numbered channels were loaded with GABA solutions (G) of increasing concentration (subscript denotes concentration in μM). Odd-numbered channels were loaded with external bath solution (E). Shown below the device are the corresponding currents (normalized to the 1000 μM trace) evoked from lifted whole cells expressing rat α4β3γ2L GABA_A receptors. One-second GABA applications were separated by 45-s washes in external solution to allow for complete agonist unbinding (omitted traces indicated by //). Following exposure to the final GABA solution (channel 12), neurotransmitter washout was accomplished by stepping the device in reverse to channel 11 (indicated by light gray box; far right). (b) As above, except that even-numbered channels contained either low (10 μM; lanes 2, 4, and 6) or high (100 μM; lanes 8, 10, and 12) concentrations of GABA along with either a putative agonist or antagonist (PB = pentobarbital; TH = THDOC; PX = picrotoxin; BI = bicuculline; subscript denotes concentration in μM). Agonists (PB and TH) and antagonists (PX and BI) were co-applied with 10 and 100 μM GABA, respectively. Dashed lines indicate control peak current amplitudes for reference.