Multimodal antidepressant vortioxetine increases frontal cortical oscillations unlike escitalopram and duloxetine – a quantitative EEG study in rats

BACKGROUND AND PURPOSE: EEG studies show that 5-HT is involved in regulation of sleep–wake state and modulates cortical oscillations. Vortioxetine is a 5-HT(3), 5-HT(7), and 5-HT(1D) receptor antagonist, 5-HT(1B) partial agonist, 5-HT(1A) agonist, and 5-HT transporter inhibitor. Preclinical (animal) and clinical studies with vortioxetine show positive impact on cognitive metrics involving cortical function. Here we assess vortioxetine's effect on cortical neuronal oscillations in actively awake rats. EXPERIMENTAL APPROACH: Telemetric EEG recordings were obtained with the following treatments (mg·kg(−1), s.c.): vehicle, vortioxetine (0.1, 1.0, 3.0, 10), 5-HT(1A) agonist flesinoxan (2.5), 5-HT(3) antagonist ondansetron (0.30), 5-HT(7) antagonist SB-269970-A (10), escitalopram (2.0), duloxetine (10) and vortioxetine plus flesinoxan. Target occupancies were determined by ex vivo autoradiography. KEY RESULTS: Vortioxetine dose-dependently increased wakefulness. Flesinoxan, duloxetine, ondansetron, but not escitalopram or SB-269970-A increased wakefulness. Quantitative spectral analyses showed vortioxetine alone and with flesinoxan increased θ (4–8 Hz), α (8–12 Hz) and γ (30–50 Hz) power. Duloxetine had no effect on θ and γ, but decreased α power, while escitalopram produced no changes. Ondansetron and SB-269970 (≈31–35% occupancy) increased θ power. Flesinoxan (≈41% occupancy) increased θ and γ power. CONCLUSIONS AND IMPLICATIONS: Vortioxetine increased wakefulness and increased frontal cortical activity, most likely because of its 5-HT(7) and 5-HT(3) antagonism and 5-HT(1A) agonism. Vortioxetine differs from escitalopram and duloxetine by increasing cortical θ, α and γ oscillations. These preclinical findings suggest a role of vortioxetine in modulating cortical circuits known to be recruited during cognitive behaviours and warrant further investigation as to their clinical impact.