Differential role of AMPA receptors in mouse tests of antidepressant and anxiolytic action.

Depression and anxiety often co-occur, and conventional monoamine-facilitating antidepressants show efficacy against symptoms in both disorders. Rodent studies indicate that antidepressant effects of monoamine-based antidepressants involve increased α-amino-3-hydroxy-5- methyl-4-isoxazolepropionic acid glutamate receptor (AMPAR) neurotransmission, and positive allosteric modulators (PAMs) at AMPARs produced antidepressant-like effects in rodents. While this suggests that increased AMPAR-mediated neurotransmission is beneficial in depression management, preclinical studies addressing AMPARs in relation to anxiety have given ambiguous results with both anxiolytic-like and anxiogenic-like effects observed after AMPAR blockade. This study systematically compared the effects of the AMPAR potentiator LY451646 and the AMPAR antagonist GYKI-53655 on depression-related behaviour using the mouse forced swim (FST) and tail suspension tests (TST), and anxiety-related behaviour using the elevated zero maze (EZM), marble burying (MB) and novelty-induced hypophagia (NIH) tests. The serotonin-selective antidepressant citalopram was included for comparison. Due to the importance of AMPARs in learning and memory we also tested if GYKI-53655 disrupted performance in the V-maze test for attention-dependent behaviour, and the social transmission of food preference (STFP) test of long-term memory. LY451646 (3 mg/kg) showed an antidepressant-like profile in the FST and TST, and GYKI-53655 (≥ 5 mg/kg) had a depressogenic-like effect in the TST but no effect in the FST. Conversely, GYKI-53655 produced marked anxiolytic-like effects in the EZM (≥ 2.5 mg/kg), MBT (≥ 2.5 mg/kg), and NIH tests (≥ 5 mg/kg), while LY451646 (≥ 3 mg/kg) increased anxiety-like behaviour in the EZM. Citalopram showed an antidepressant-like effect in the FST (≥ 10 mg/kg), but not TST, an anxiolytic-like effect in the EZM (≥ 3 mg/kg) and MB test (≥ 2.5 mg/kg), and an anxiogenic-like effect in the NIH test (≥ 30 mg/kg). GYKI-53655 did not affect cognitive performance in the V-maze or STFP tests. Collectively, these findings suggest a differential role of AMPARs in depression and anxiety, with AMPAR activation promoting antidepressant responses and AMPAR inhibition promoting anxiolytic responses. The potential of AMPARs as a novel target in depression and anxiety pharmacotherapy is discussed.