Figure 5

Effects of vmPFC HFS on DRN neuronal firing. (a) Excitatory and inhibitory effects on putative 5-HT DRN neurons (n=18) firing rate changes before, during and after vmPFC HFS. Darkened zone area indicates stimulation period (100 Hz, 100 μA, 100 μs). Firing rate was quantified during the final 60 s before stimulation as control baseline, during the second and fifth minute of vmPFC HFS, and on the fifth minute following cessation of vmPFC stimulation. Note, both excitatory and inhibitory effects on the firing rates of 5-HT neurons were observed by vmPFC HFS. (b) Photomicrographs showing immunohistochemical characterization of a neurobiotin (NB) juxtacellular-labeled 5-HT immunopositive neuron in the rat DRN. Scale bar, 20 μm at × 40 magnification. (c) A triphasic extracellular waveform shape with a broad spike width typically used to indicate for 5-HT neuron. (d and f) Spike trains and mean firing rate (15-s bins) of 5-HT putative neurons, before, during and after 5 min HFS of the vmPFC. Darkened zone areas indicate stimulation period (second and fifth minute of vmPFC HFS). Plot of percentage excitation (e) and inhibition (g) during the fifth minute after vmPFC HFS against baseline firing rates. Significant difference from the baseline levels ^*P<0.05. 5-HT, 5-hydroxytryptamine, serotonin; DRN, dorsal raphe nucleus; HFS, high-frequency stimulation; vmPFC, ventromedial prefrontal cortex.