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47
OM&P
Section CELLULAR NEUROSCIENCE
Acknowledgements
This work was supported by Program "Molecular and Cell Biology" and grant Russian Science Foundation (14-15-00942). References
1. C. Suter-Crazzolara, K.Unsicker, Neuroreport, 1994, 5, 2486-2488.
2. N. Kust, D. Panteleev, I. Mertsalov, et al., Mol Neurobiol., 2015,51(3),1195-1205.
Excitation-Energy Coupling and Vesicle-Based Signaling in Astrocytes
Nina Vardjan, Marko Kreft, Helena H. Chowdhury, Anemari Horvat, Matjaz Stenovec, Eva Lasic, Marjeta Lisjak, Bostjan Rituper, Jernej Jorgacevski, Maja Potokar, Mateja Gabrijel, Robert Zorec*
Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia, Celica BIOMEDICAL, Lab Cell Engineering, Ljubljana, Slovenia. * Presenting e-mail: [email protected]
Astrocytes, a heterogeneous glial cell type, get excited when neurotransmitters, such as noradrenaline (NA) and ATP bind to their membrane receptors and respond back by releasing their own signals. This involves vesicles, which store chemicals termed gliotransmitters or more generally gliosignaling molecules. In the former case chemical messengers get released from astrocytic sites proximal to the synapse, which defines communication to occur in the micro-space of contact between the synapse and the astrocyte. In contrast gliosignaling molecules may also be released into the extracellular space and get transported to locations far away from the active astrocyte. This mode of release resembles the endocrine system. Hence astrocytes are considered to be part of the gliocrine system in the brain, where the glymphatic system mediates the convection of released molecules. This complex system not only plays a role in cell-to-cell communication but also synchronizes the provision of energy for neural networks. Astrocytes contain glycogen, a form of energy store. Excitation of astrocytes by volume transmitters, such as NA, released by locus coeruleus neurons, activates adrenergic receptors and stimulates glycogenolysis, providing lactate. This lecture will discuss how astrocytes operate to synchronize excitation and energy provision. Moreover, Ca2+ -dependent fusion of the vesicle membrane with the plasma membrane in astrocytes will be presented.
Using an approach to study single astrocytes by quantitative imaging confocal microscopy, we studied how stimuli like noradrenaline or ATP activate cytosolic calcium signals and how the mobility of fluorescently labelled secretory vesicles is affected by physiological states of astrocytes. By fluorescence resonance energy transfer (FRET) nanosensors we also measured second messenger cAMP and metabolites, such as D-glucose and L-lactate. Stimulation of astrocytes by noradrenaline increases cytosolic calcium and cAMP in distinct time-domains. Vesicle mobility was differentially modulated, depending of the vesicle cargo, by elevations in cytosolic calcium levels. NA also stimulated glycolysis monitored as an increase in FRET-based cAMP and cytosolic L-lactate increase, while cytosolic D-glucose levels were decreased due to facilitated consumption in glycolysis.It is proposed that excited astrocytes liberate energy by enhanced glycolysis, while a complex vesicle -ased signalling response is taking place in the same time domain. Hence, excitation-energy coupling is time-associated with alterations in astrocytic vesicle-based communication capacity.
Offline Effects of Single and Paired Pulse TMS
Evgeni Blagovechtchenski*, Tommaso Fedele, Maria Nazarova, Vadim Nikulin
Saint-Petersburg State University, Russia. * Presenting e-mail: [email protected]
All effects produced by TMS are mainly two types: online or offline. Online TMS effects (behavior and electrophysiological) described as lasting less than 1 second after stimulation. Offline TMS on the other hand means that the stimulation effects lasting seconds and minutes. Single and paired plus (ppTMS) stimulations are considered as online (Terao et.al.,
12 Opera Med Physiol 2016 Vol. 2 (S1)
