The consequences of long term antidepressant treatment
Chronic administration of antidepressants can cause a number of changes in the brain, depending on the particular drug type: (1) SSRIs and MAOIs desensitize inhibitory 5-HT1A somatodendritic receptors and inhibitory pre-synaptic 5-HT1D autoreceptors. They can also prevent the uptake of 5-HT into the nerve terminal by binding to the imipramine binding site (2) TCA, electroconvulsive therapy (ECT) and other non-SSRI antidepressants can sensitize inhibitory post-synaptic 5-HT1A receptors and can reduce the expression of stimulatory 5-HT2A receptors. (3) Experimental evidence suggests that chronic antidepressant treatment can also affect post-receptor signalling mechanisms, such as G-proteins.
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References
Psychotropic drugs that modify the serotonergic system. In: Fundamentals of psychopharmacology, 2nd edition. Leonard B. Chichester, England. John Wiley and Sons, 1997: 91–105.