Fig. 4. The effects of hyperosmotic stimulation and application of FFA or Ni²⁺ on spontaneous action potential firings in AVP neurons. (a, b) Representative records of spontaneous action potential firings under isosmotic (Iso) or hyperosmotic (Hyper) conditions and before and after application of FFA (a: +FFA, n=8) or Ni²⁺ (b: +Ni²⁺, n=10). Insert panels given below the traces of membrane potential changes represent expanded traces for the indicated parts of the records for 30 s. Arrows represent the membrane potential level of −50 mV. (c) The averages of the firing frequency (Hz) under isosmotic (Iso) or hyperosmotic (Hyper) conditions in the absence and presence of FFA, Ni²⁺ or ω-CgTx (n=8-27). *p<0.05 vs. Iso. ^#p<0.05 vs. Hyper in the absence of blockers.