Selective serotonin reuptake inhibitors (SSRI) are used to treat depression, however, for many patients these are only minimally effective. The question is, why? A group of researchers at the School of Medicine at the University of Texas Health Science Center in San Antonio have been addressing this issue. They have found secondary sites involved with serotonin reuptake and have developed a synthetic compound (decynium-22) that interacts with these other reuptake components. Having knowledge of these other components will enable pharmaceuticals to be developed to enhance the effect of SSRIs. This study was reported in the June 18 issue of The Journal of Neuroscience.
Serotonin is a neurotransmitter associated with a sense of well-being. Low levels of serotonin leads to depression, anxiety, obsessive compulsive disorder, headaches, over eating and obesity. To try to boost serotonin levels, doctors often prescribe SSRI treatment. These drugs inhibit the reuptake of serotonin in the synaptic cleft allowing what little serotonin there to remain around longer and boost the transmitter signal. Essentially, this should boost a sense of well-being. However, for many patients this is not the case.
It is now known that there are other reuptake systems beyond the classically known SSRI system. Therefore, current drug therapies have not been able to address this issue. According to Dr. Lyn Daws (professor of physiology and pharmacology) at the University of Texas Health Science Center San Antonio, “Until now we did not appreciate the presence of backup cleaners for serotonin.” She goes on further to say that, “We were not the first to show their presence in the brain, but we were among the first to show that they were limiting the ability of the SSRIs to increase serotonin signaling in the brain. The study described in this new paper is the first demonstration of enhancing the antidepressant-like effect of an SSRI by concurrently blocking these backup vacuum cleaners.”
Given that SSRIs block the reuptake of serotonin, the other systems — now known as organic cation transports — keep a ceiling on how high serotonin levels can rise which certainly limits the therapeutic value of currently administered drugs.
The new compound they have developed, decynium-22, will help to identify these new organic cation transport systems and aid in the development of new antidepressant drugs to assist current SSRIs.