Fig. 9.
Integrated firing rate histograms of DR serotonergic neurons after the application of DOI in mPFC (200 μm, 200 nl, shown by a 1 min bar). The neuron inA responded with an increase in firing rate after the first and second application of DOI (note the persistence of the increased firing rate), whereas the neuron in B was unaffected by the application of two consecutive doses of DOI. The distal effect of DOI on 5-HT cell firing cannot be accounted for by drug diffusion to the DR because of the small amount of tissue affected by DOI application (0.2 μl) and the inhibitory effect of DOI on 5-HT neurons when acting on DR 5-HT2A receptors (Liu et al., 2000).