Fig. 7.

Cochlear ablation decreases the ability of 5-HT to modulate excitability in P30–P35 rat A1. A: voltage traces from an example neuron from a sham animal in response to a 100 pA depolarizing current step under different drug conditions (as in Fig. 1). Dashed gray lines indicate resting membrane potential; current injection is shown below the voltage traces. B: voltage traces as in A from an example neuron from a cochlear-ablated animal. C: mean firing rates evoked by depolarizing current injections inform a population of sham rats: aCSF (squares), in the presence of 50 μM 5-HT (blue squares), after wash1 (open squares with dashed line), in 1 μM KTS (green squares), and in KTS + 5-HT (red squares). Serotonin acutely decreased the firing rate, but also had a strong delayed effect after 15 min of aCSF wash, greatly raising threshold and decreasing the firing rage. Subsequent challenges with KTS and 5-HT had no further effect. D: data for cochlear-ablated rats, in the same format as that for C. 5-HT had no acute or delayed effect. KTS decreased firing slightly, whereas the subsequent addition of 5-HT decreased firing further.