Mechanism of action of serotonin selective reuptake inhibitors. Serotonin receptors and pathways mediate therapeutic effects and side effects

J Affect Disord. 1998 Dec;51(3):215-35. doi: 10.1016/s0165-0327(98)00221-3.


Serotonin selective reuptake inhibitors (SSRIs) are currently among the most frequently prescribed therapeutic agents in all of medicine. Their therapeutic actions are diverse, ranging from efficacy in depression to obsessive-compulsive disorder, panic disorder, bulimia and other conditions as well. The plethora of biological substrates, receptors and pathways for serotonin are candidates to mediate not only the therapeutic actions of SSRIs, but also their side effects. Specifically, the immediate actions of SSRIs are mostly side effects, and may be mediated by the initiating actions of SSRIs, namely negative allosteric modulation of the serotonin transporter. A leading hypothesis to explain these immediate side effects is that serotonin is increased at specific serotonin receptor subtypes in discrete regions of the body where the relevant physiologic processes are regulated. Desensitization of post-synaptic receptors in these same discrete brain regions may explain the development of tolerance to these same side effects. The explanation for therapeutic effects characteristic of SSRIs may be found in delayed neurochemical adaptations. A leading hypothesis for this action is desensitization of somatodendritic serotonin 1A autoreceptors in the midbrain raphe. The hypothesis to explain why SSRIs have such diverse therapeutic actions is that somatodendritic 5HT1A autoreceptor desensitization increases serotonin in those critical brain regions and at those key serotonin receptor subtype(s) which may mediate the pathophysiologies of the various disorders. Understanding the topography of serotonin receptor subtypes in discrete anatomical pathways may enhance our understanding of both the therapeutic actions and side effects of these important pharmaceutical agents.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Autoreceptors / drug effects
  • Autoreceptors / physiology
  • Bulimia / drug therapy
  • Bulimia / physiopathology
  • Depressive Disorder / drug therapy
  • Depressive Disorder / physiopathology
  • Depressive Disorder / psychology
  • Down-Regulation / drug effects
  • Down-Regulation / physiology
  • Humans
  • Mental Disorders / drug therapy*
  • Mental Disorders / physiopathology
  • Mesencephalon / drug effects
  • Mesencephalon / physiology
  • Neural Pathways / drug effects
  • Neural Pathways / physiology
  • Obsessive-Compulsive Disorder / drug therapy
  • Obsessive-Compulsive Disorder / physiopathology
  • Panic Disorder / drug therapy
  • Panic Disorder / physiopathology
  • Raphe Nuclei / drug effects
  • Raphe Nuclei / physiology
  • Receptors, Serotonin / drug effects*
  • Receptors, Serotonin / physiology
  • Selective Serotonin Reuptake Inhibitors / adverse effects
  • Selective Serotonin Reuptake Inhibitors / pharmacology*
  • Selective Serotonin Reuptake Inhibitors / therapeutic use
  • Serotonin / physiology


  • Autoreceptors
  • Receptors, Serotonin
  • Serotonin Uptake Inhibitors
  • Serotonin