Antidepressants Rescue Stress-Induced Disruption of Synaptic Plasticity via Serotonin Transporter-Independent Inhibition of L-Type Calcium Channels.

Background: Long-term synaptic plasticity is a basic ability of the brain to dynamically adapt to external stimuli and regulate synaptic strength and ultimately network function. It is dysregulated by behavioral stress in animal models of depression and in humans with major depressive disorder. Antidepressants have been shown to restore disrupted synaptic plasticity in both animal models and humans; however, the underlying mechanism is unclear.
Methods: We examined modulation of synaptic plasticity by selective serotonin reuptake inhibitors (SSRIs) in hippocampal brain slices from wild-type rats and serotonin transporter (SERT) knockout mice. Recombinant voltage-gated calcium (Ca ²⁺ ) channels in heterologous expression systems were used to determine the modulation of Ca ²⁺ channels by SSRIs. We tested the behavioral effects of SSRIs in the chronic behavioral despair model of depression both in the presence and in the absence of SERT.
Results: SSRIs selectively inhibited hippocampal long-term depression. The inhibition of long-term depression by SSRIs was mediated by a direct block of voltage-activated L-type Ca ²⁺ channels and was independent of SERT. Furthermore, SSRIs protected both wild-type and SERT knockout mice from behavioral despair induced by chronic stress. Finally, long-term depression was facilitated in animals subjected to the behavioral despair model, which was prevented by SSRI treatment.
Conclusions: These results showed that antidepressants protected synaptic plasticity and neuronal circuitry from the effects of stress via a modulation of Ca ²⁺ channels and synaptic plasticity independent of SERT. Thus, L-type Ca ²⁺ channels might constitute an important signaling hub for stress response and for pathophysiology and treatment of depression.
(Copyright © 2017 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)