5-HT caused increased excitability in SNs of mature but not aged II Aplysia.
A) Membrane potential in SNs in response to 5-HT (20 μM) perfusion onto the pleural-pedal ganglion. B) 3 min of 5-HT significantly depolarized mature but not aged II tail SNs. * denotes significant difference from ASW control at p≤0.05 via paired t-test. C) Injection of 3 ms depolarizing current evoked a single AP in tail SNs that was compared before (ASW) and after 5-HT treatment. D) AP duration increased significantly in mature but not aged II tail SNs after 3 min 5-HT. * denotes significant difference from ASW control at p≤0.05, paired t-test (n = 25 for mature, n = 23 for aged II).