A surprising source of serotonin could affect antidepressant activity
News Mar 30, 2015
Depression affects an estimated 350 million people worldwide and poses a major public health challenge, according to the World Health Organization. Researchers have discovered an unconventional way that serotonin is released from neurons that could play an important role in the mechanism through which antidepressant drugs work. The Journal of General Physiology study is highlighted in the April issue.
Serotonin is a chemical in the brain that plays a key role in regulating various emotions and behaviors. Like other neurotransmitters, which relay signals between neurons, serotonin is stored in vesicles in the presynaptic terminal of one neuron and released into the synapse in response to neuronal firing to bind to receptors on a postsynaptic neuron. An imbalance in serotonin signaling is generally thought to contribute to depression.
Selective serotonin reuptake inhibitors (SSRIs) are a class of antidepressants that increase levels of extracellular serotonin by preventing its reuptake by neurons. However, one of the main drawbacks of SSRIs is their delayed effect. A contributing factor to the delay is thought to be that the firing of serotonergic neurons is itself suppressed by extracellular serotonin, which acts on inhibitory neuronal "autoreceptors" in a process known as autoinhibition. Thus, SSRIs -- which are intended to enhance serotonin signaling -- may actually initially slow the therapeutic process.
Now, Boris Mlinar and colleagues from the University of Florence show that, remarkably, the serotonin that mediates autoinhibition appears to be released into the extracellular space through a distinct process. Rather than being released from vesicles in response to neuronal firing (in a process known as exocytosis), the study indicates that this pool of serotonin may be supplied by simple diffusion across the cell membrane. Mlinar and colleagues believe that a full understanding of this process might inform better strategies of modulating serotonin signaling in order to treat depression.
Note: Material may have been edited for length and content. For further information, please contact the cited source.
B. Mlinar, A. Montalbano, G. Baccini, F. Tatini, R. B. Palmini, R. Corradetti. Nonexocytotic serotonin release tonically suppresses serotonergic neuron activity. The Journal of General Physiology, Published February 23 2015. doi: 10.1085/jgp.201411330
Molecules in Spit Could Help Diagnose ConcussionsNews
Diagnosing a concussion can sometimes be a guessing game, but clues taken from small molecules in saliva may be able to help diagnose and predict the duration of concussions in children, according to Penn State College of Medicine researchers.READ MORE
Elpis BioMed Closes Funding Round to Commercialise Novel Technology Platform for Generating Human Cell TypesNews
New Cambridge spin-out company commercialises disruptive technology that enables rapid generation of pure and consistent batches of human cell types. Geographically diversified, top-tier investor team includes key industry leaders to support early company development.READ MORE
Study: Non-fearful social withdrawal linked positively to creativityNews
Newly published research by a University at Buffalo psychologist suggests that not all forms of social withdrawal are detrimental.READ MORE