How serotonin and noradrenaline affect the brain in depression

Several classes of antidepressant drugs increase synaptic levels of noradrenaline and serotonin.

• Antidepressant drugs are categorized into three families: monoamine reuptake inhibitors, monoamine oxidase inhibitors, and monoamine receptor antagonists.
• All classes aim to elevate the synaptic concentrations of noradrenaline and serotonin, which work together to produce antidepressant effects.
• The delayed onset of antidepressant action may be linked to the initial activation of inhibitory autoreceptors that reduce neurotransmitter levels.
• Desensitization of these autoreceptors over time could lead to a more pronounced antidepressant response.
• Antagonists at these autoreceptors, such as pindolol, are proposed as potential adjuncts to improve the speed of clinical response, though evidence is mixed.
• Central monoamine depletion studies suggest that the therapeutic effects of antidepressants are primarily due to increased synaptic monoamine levels.

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