Clomipramine increases firing rate in lateral septal neurons related with hippocampus

Long-term clomipramine administration (CMI: 2.5 mg/kg IP, 25 days) effects on 274 identified hippocampus-septal neurons was assessed in rats. Stimulation of CA 1/dentate areas produced a biphasic response in 61% of lateral septal neurons. A brief activation was followed by a period of suppression of firing. In CMI-treated rats, the neurons showing this biphasic response increased their firing rate about fourfold, while the suppression of firing shortened around threefold. Other septal neurons (36%), in which only the burst of activation appeared but not suppression of firing, did not change their firing rate even after long-term CMI. In conclusion, CMI produces an increase of firing rate in lateral septal neurons receiving inhibitory hippocampal influence which is likely to be mediated by a disinhibitory process.