Synaptic Dysfunction in Depression: Potential Therapeutic Targets

Depression involves shrinkage of brain regions that regulate mood and cognition, such as the prefrontal cortex and hippocampus, along with reduced neuronal synapses in those areas. Typical antidepressants can reverse some of these deficits but work slowly and have limited effectiveness. Ketamine, a drug that blocks N-methyl-D-aspartate receptors, rapidly (within hours) improves symptoms in patients who do not respond to standard antidepressants. In basic studies, ketamine quickly promotes the formation of new synapses and reverses the synaptic damage caused by chronic stress. These findings suggest that maintaining healthy mood circuit connections is central to depression and its treatment, forming the basis of a synaptogenic hypothesis.

Study at a glance

Abstract

Basic and clinical studies demonstrate that depression is associated with reduced size of brain regions that regulate mood and cognition, including the prefrontal cortex and the hippocampus, and decreased neuronal synapses in these areas. Antidepressants can block or reverse these neuronal deficits, although typical antidepressants have limited efficacy and delayed response times of weeks to months. A notable recent discovery shows that ketamine, a N-methyl-D-aspartate receptor antagonist, produces rapid (within hours) antidepressant responses in patients who are resistant to typical antidepressants. Basic studies show that ketamine rapidly induces synaptogenesis and reverses the synaptic deficits caused by chronic stress. These findings highlight the central importance of homeostatic control of mood circuit connections and form the basis of a synaptogenic hypothesis of depression and treatment response.