Biophysical Society Thematic Meeting| Padova 2019

Quantitative Aspects of Membrane Fusion and Fission

Poster Abstracts

50-POS Board 50 KETAMINE EVOKES VESICLE FUSION PORE NARROWING AND FLICKERING IN ASTROCYTES Matjaz Stenovec 1,2 ; Eva Lasic 1 ; Boštjan Rituper 1 ; Jernej Jorgacevski 1,2 ; Marko Kreft 1,2,3 ; Robert Zorec 1,2 ; 1 University of Ljubljana, Faculty of Medicine, Institute of Pathophysiology, Ljubljana, Slovenia 2 Celica Biomedical, Cell Engineering Laboratory, Ljubljana, Slovenia 3 University of Ljubljana, Biotechnical Faculty, Department of Biology, Ljubljana, Slovenia Ketamine, a dissociative anesthetic, elicits analgesic, psychotomimetic and rapid antidepressant effects that are of particular neuropharmacological interest in psychiatry. Recent studies in astrocytes revealed that prolonged ketamine application reduces Ca 2+ signaling and exocytotic release of gliotransmitters. Here high-resolution cell-attached membrane capacitance measurements were used to examine at single vesicle level how ketamine affects the interaction between the vesicle and the plasmalemma in cultured rat astrocytes. Ketamine evoked long- lasting epochs of repetitive opening and closing of the vesicle fusion pore, termed bursts that were both time- and concentration-dependent. These were recorded following an acute application of anesthetic dose (25 µM) and a 30 min application of (sub)anesthetic doses (0.025- 25 µM) of ketamine. In these bursts, unitary fusion pore openings were characterized by a decreased fusion pore conductance, indicating that the fusion pore was stabilized in a narrow configuration, too narrow to allow the passage of relatively large gliotransmitters, such as BDNF reported previously (Stenovec et al. 2015). Ketamine-evoked increase in burst occurrence correlated well with a decreased occurrence of full vesicle fissions, indicating that narrow fusion pore predominantly hindered the retrieval of vesicles into endocytotic pathway. While the nature of this, by now unrecognized, mechanism of ketamine treatment in astroglia is unknown, it may play a role in vesicular release and (re)uptake of molecules, and possibly contributes to the powerful ketamine antidepressant action in patients suffering from major depressive disorder.

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