Electrophysiological Investigations on the Role of Selected Serotonin Receptors and the Serotonin Transporter on Serotonin Transmission in the Rat Brain

This study assessed the in vivo effects of various serotonin (5-HT) receptor modulators on 5-HT neurotransmission in the rat hippocampus. Vortioxetine, humanized-vortioxetine, and escitalopram blocked the 5-HT transporter, but similar to ipsapirone did not dampen the sensitivity of postsynaptic 5-HT1A receptors. Long-term administration of all treatments increased the tonic activation of postsynaptic 5-HT1A heteroreceptors, an effect common to all antidepressants. Vortioxetine decreased the function of the terminal 5-HT1B autoreceptor under high but not a low degree of activation, thus showing that its partial agonism led to increased 5-HT release and that long-term administration results in the desensitization of terminal 5-HT1B autoreceptors. Vortioxetine overcame the effects of 5-HT1B and 5-HT3 receptor agonists. This study was unable to determine the involvement of 5-HT7 receptor antagonism exerted by vortioxetine affects 5-HT neurotransmission. Therefore, vortioxetine would appear to exert different actions, via transporter and receptor activity, on the serotonergic system in the hippocampus, consistent with its unique pharmacological profile