Interaction of the serotonergic and the immune systems: 5HT-moduline

The serotonergic system is known as a neuromodulatory system present in the brain and participating to the homeostasis of the brain. Its major morphol ogical and anatomical features are favoring this role. Accordingly it is in volved in many physiological functions and a number of psychiatric dysfunct ions. Amongst the numerous receptors involved in its functions, 5HT(1B) rec eptors constitute a particular subtype located on neuron terminals and regu lating the release of the corresponding neurotransmitter. These receptors a re specifically the target: of an endogenous tetrapeptide (5HT-Moduline) ch aracterized in mammalian brain and regulating the functional activity of th e receptor as an allosteric modulator. Immunocompetent cells were shown to also contain 5HT(1B) receptors using mo lecular biology, immunocytochemistry and pharmacology. These receptors part icipate to the control of transcriptional activity of immediate early genes , and stimulate the proliferation of cells. 5HT-Moduline also interacts wit h the function of 5HT(1B) receptor at this level, playing an antagonistic r ole. The observed results indicate that the serotonergic system not only exerts a neuromodulatory role in central nervous tissue but presumably also contro ls the activity of immunocompetent cells. The serotonergic system may be in volved in the reciprocal neuroimmune relationships via mechanisms which imp licate 5HT(1B) receptors and their allosteric modulator 5HT-Moduline.