International Journal of Livestock Research ISSN 2277-1964 ONLINE Vol 4(7) Oct’14 Hosted@www.ijlr.org DOI 10.5455/ijlr.20140726083304 Page1 Energy Consumption during Synaptic Transmission - A Review Subhashree Sarangi*, A. P. K. Mahapatra, A. K. Kundu and S. Mohapatra Department of Veterinary Physiology, College of Veterinary Science & Animal Husbandry, Orissa University of Agriculture & Technology, Bhubaneswar-751003, Odisha, INDIA *Corresponding author: subhashreesarangi2010@gmail.com Rec. Date: Jul 11, 2014 01:59 Accept Date: Jul 26, 2014 20:33 Published Online: October 22, 2014 DOI 10.5455/ijlr.20140726083304 Abstract Enormous progress has been made in understanding synaptic transmission and its related plasticity. The development in the field of applied research has been possible due to the use of new tools and technology that has led to a detailed understanding of Ca2+-triggering of neurotransmitter release and other key mechanisms behind synaptic plasticity which when incorporated in the field of veterinary research can prove quite significant and efficacious. We will review how most brain energy is used on synapses, investigate how pre- and postsynaptic terminals are optimized to maximize information transmission at minimum energy cost, and assess how ATP provision to synapses is regulated to satisfy their energetic needs. We then consider how synapse energy use changes with development and synaptic plasticity, and between awake and sleep active zone states. Key words: Active Zone, Dendritic Spines, Presynaptic Plasticity, Post Synaptic Signalling, Sleep, Synapse Introduction The number of neurons in the central nervous system of mammals varies greatly and it is more than 100 billion in a human being (Guyton and Hall, 2006) Incoming signals enter the neuron through synapses located mostly on the neuronal dendrites, and also on the cell body. Conversely, the output signal travels by way of a single axon leaving the neuron. Then, this axon has many separate branches to other parts of the nervous system or peripheral body. The passage of signal is normally only in the forward direction (from the axon of a preceding neuron to dendrites on cell membranes of subsequent neurons). Building on the classical physiological work by Katz and Eccles in the 1940s (Eccles J. C., 1945), major advances in the past two decades have elucidated how synapses work molecularly and how neuronal computation is energetically expensive. Consequently, the brain’s limited energy supply imposes constraints on its information processing capability. A recent study suggests that balanced synaptic currents have the highest coding efficiency and the highest energy efficiency (Sengupta et al., 2013). Most brain energy is used on synaptic transmission, making it important to understand how energy is provided to and used by synapses. Recent findings suggest that Ca 2+ -clearance, transmitter uptake and vesicle recycling/refilling have similar contribution to ion fluxes and energy demand of synaptic transmission at the Schaffer-collateral synapse as presynaptic action potentials (Liotta et al., 2012).