Septal neurons related with hippocampus increase their firing rate after long-term clomipramine.

In the rat, long-term clomipramine increases the firing rate in lateral septal neurons. Although the hippocampus is the main afference for septal nuclei, it is unknown whether clomipramine increases the firing rate in most of hippocampal-septal neurons. Therefore, the present study explored the actions of long-term clomipramine in lateral septal neurons identified by their relation to the hippocampus. In most recordings, hippocampal stimulation produced a brief excitatory short-latency response, followed by a period of inhibition of firing. These neurons increased their firing rate after clomipramine treatment. Other septal neurons not respondent to hippocampal stimulation did not respond to clomipramine treatment, either. We concluded that only hippocampal-septal neurons are clomipramine responders too, and the drug-induced enhancement of firing rate is likely to be mediated by an interneuron-mediated disinhibition process.