Repeated administration of citalopram and imipramine alters the responsiveness of rat hippocampal circuitry to the activation of 5-HT7 receptors.

The effects of a selective serotonin reuptake inhibitor, citalopram, and a tricyclic antidepressant drug, imipramine, administered repetitively for 14 days, were investigated ex vivo in rat hippocampal slices. Spontaneous epileptiform bursts were recorded from the CA3 area in nominally Mg(2+)-free incubation conditions. 5-carboxamidotryptamine (5-CT) dose-dependently increased bursting frequency in the presence of N-[2-[4-(2-methoxyphenyl)-1 piperazinyl]ethyl]-N-2-pyridinylcyclohexanecarboxamide (WAY 100635). This effect could be dose-dependently blocked by (2R)-1-[(3-Hydroxyphenyl)sulfonyl]-2-[2-(4-methyl-1-piperidinyl)ethyl]pyrrolidine hydrochloride (SB 269970), thus implicating the involvement of 5-HT(7) receptors. Repeated treatment with citalopram or imipramine resulted in an attenuation of the excitatory effects of the activation of hippocampal 5-HT(7) receptor.