Monitoring changes in membrane potential elicited by FMRFamide and PSEM89S. A, Voltage response to a 100-ms puff of PSEM89S (500 μm) in an isolated HC recorded with the gramicidin perforated patch configuration. A puff was delivered at the time indicated by the arrow. Although the concentration of PSEM89S was 500 μm in the pipette, the concentration of the drug is estimated to be diluted ∼50-fold at the cell (Firestein and Werblin, 1989), positioned ∼100 μm from the puffer pipette. B, Traces from three different HCs showing responses to 100-ms puffs of GABA (1 mm), chosen to highlight the variability of responses to GABA that were observed between cells. C, Response to 100-ms application of muscimol (100 μm), a GABAA receptor agonist. Responses were uniformly hyperpolarizing in all cells tested. D, Summary data showing the resting membrane potential, and the membrane potential at the peak of the response to PSEM89S. Large bolded symbols are the mean ± SEM for each condition (n = 6). E, Summary of the change in membrane potential evoked by puffs of GABA or muscimol. Small closed symbols are the responses of individual cells to GABA (n = 11). Open symbols are the responses to muscimol (n = 7). Open boxes are the mean ± SEM for hyperpolarizing responses, and the shaded box is the mean ± SEM for depolarizing responses. The mean amplitude of the responses evoked by muscimol was not significantly different from the amplitude of hyperpolarization evoked by GABA (p = 0.53, rank-sum test). F, Summary data for bath application of FMRFamide (30 μm). Large bolded symbols are the mean ± SEM for each condition (n = 7).
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