(A) Representative recordings of glutamate responses of a type 4 OFF CBC, clamped to –60 mV. The experimental setup (A₁) and an image of the lucifer yellow-filled recorded cell (A₂) are shown to the left. (A₃) Application of NO donor NOC-12 (200 μM) only affected the slow component of the glutamate response, by shortening the duration of the electrical response. Bars indicate the stimulus duration. (A₄) Bar diagrams displaying the mean ± SEM of the total charge transferred during the glutamate response, with and without NO stimulation. (A₅) The maximum amplitude of the glutamate response, measured at the peak of the fast component, remained unaffected by NO. (B) Control experiments with puffs of extracellular solution instead of NOC-12 were ineffective, demonstrating the absence of stimulus or pressure artifacts. (C) Bath application of the GABA_A and GABA_C receptor antagonists SR-95531 and TPMPA, and the glycine receptor blocker strychnine did not affect the modulation of the glutamate response by NO in type 4 CBCs. Image scale bars = 10 μm; ns = not significant.

https://doi.org/10.1371/journal.pone.0119399.g001