<h3>Title</h3>
<p><span style="color: #0000ff;">Vesicular membrane “reads” the intravesicular serotonin concentration to facilitate exocytosis</span></p>
<p><strong><span style="text-decoration: underline;">Abstract</span> :</strong></p>
<p style="text-align: justify;">Neurotransmission is an essential process through which neurons communicate their signals to target cells. Chemical neurotransmission involves the release of neurotransmitter in multiples of a fixed amount (quantum) of the neurotransmitter, a process termed as quantal release. This fixed amount of neurotransmitter is packaged in membrane bound vesicles that undergo an elaborate and dynamic process, which facilitates the release of the neurotransmitter. At a given time the neuron contains vesicles filled with a varied range of neurotransmitter concentrations owing to the continuous recycling and refilling of these vesicles. However, the mechanism underlying the selection of mature vesicles that have the required neurotransmitter content for exocytosis is not known. The membrane of the vesicles forms a direct interface between the intravesicular neurotransmitter concentration and the external molecular machinery that enables exocytosis. Further, the neurotransmitter, serotonin, is known to alter the properties of the lipid bilayer membrane. We sought to determine if serotonin concentration alters membrane properties of the vesicles, which can subsequently affect their exocytosis. Using label-free multiphoton imaging for serotonin and single-photon spectral imaging for Nile red (used as a probe for measuring membrane order), we demonstrated that vesicular serotonin concentration modulates membrane order, elucidating a novel mechanism for selection of mature vesicles for exocytosis.</p>