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IBEC Seminar: J. Miguel Rubi
Friday, May 8, 2015 @ 10:00 am–11:00 am
Somatic exocytosis of serotonin mediated by molecular motors
J. Miguel Rubi, Departament de Fisica Fonamental, Universitat de Barcelona
We quantified somatic exocytosis of serotonin in Retzius neurons and explored the possible contribution of molecular motors and the cytoskeleton on the mobilization of vesicles induced by stimulation with trains of electrical impulses. Secretion was quantified from the increase of fluorescence of FM1-43 in response to sequences of 20 mV trains of 10 impulses at 2 min intervals, produced by intracellular current injection. Somatic secretion was also evoked by a pulse of 10 mM caffeine applied to the bathing solution. Stimulation of neurons produced a gradual increase in FM1-43 fluorescence for over the next five minutes. The kinetics and latencies of these increases varied from one neuron to another but usually maintaining a sigmoidal shape in one or two steps. Neurons stimulation in the presence of colchicine to uncouple microtubules, failed to evoke fluorescence increases, thus suggesting that vesicle mobilization depended on tubulin-based motor. The kinetics of the fluorescence increases of individual neurons was accounted for by using a model based on a diffusion equation in the presence of external forces, consistent with the contribution of molecular motors to the mobilization of the vesicle clusters towards the membrane in response to electrical activity. Our data show that somatic serotonin secretion in Retzius neurons depends on a motor-based cytoskeletal mobilization of vesicles induced by electrical activity.