Upregulation of transmitter release probability improves a conversion of synaptic analogue signals into neuronal digital spikes

Yu Jiandong, Qian Hao, Wang, Wang Jin-Hui

Description

Action potentials at the neurons and graded signals at the synapses are primary codes in the brain. In terms of their functional interaction, the studies were focused on the influence of presynaptic spike patterns on synaptic activities. How the synapse dynamics quantitatively regulates the encoding of postsynaptic digital spikes remains unclear. We investigated this question at unitary glutamatergic synapses on cortical GABAergic neurons, especially the quantitative influences of release probability on synapse dynamics and neuronal encoding. Glutamate release probability and synaptic strength are proportionally upregulated by presynaptic sequential spikes. The upregulation of release probability and the efficiency of probability-driven synaptic facilitation are strengthened by elevating presynaptic spike frequency and Ca 2+ . The upregulation of release probability improves spike capacity and timing precision at postsynaptic neuron. These results suggest that the upregulation of presynaptic glutamate release facilitates a conversion of synaptic analogue signals into digital spikes in postsynaptic neurons, i.e., a functional compatibility between presynaptic and postsynaptic partners.

Sujets

• Synapse
• Neuron

Informations

• Publié par: biomed
• Publié le: 01 janvier 2012
• Nombre de lectures: 3
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

Yu et al. Molecular Brain 2012, 5 :26 http://www.molecularbrain.com/content/5/1/26

R E S E A R C H Open Access Upregulation of transmitter release probability improves a conversion of synaptic analogue signals into neuronal digital spikes Jiandong Yu 1,2 , Hao Qian 1,2 and Jin-Hui Wang 1,2*

Abstract Action potentials at the neurons and graded signals at the synapses are primary codes in the brain. In terms of their functional interaction, the studies were focused on the influence of presynaptic spike patterns on synaptic activities. How the synapse dynamics quantitatively regulates the encoding of postsynaptic digital spikes remains unclear. We investigated this question at unitary glutamatergic synapses on cortical GABAergic neurons, especially the quantitative influences of release probability on synapse dynamics and neuronal encoding. Glutamate release probability and synaptic strength are proportionally upregulated by presynaptic sequential spikes. The upregulation of release probability and the efficiency of probability-driven synaptic facilitation are strengthened by elevating presynaptic spike frequency and Ca 2+ . The upregulation of release probability improves spike capacity and timing precision at postsynaptic neuron. These results suggest that the upregulation of presynaptic glutamate release facilitates a conversion of synaptic analogue signals into digital spikes in postsynaptic neurons, i.e., a functional compatibility between presynaptic and postsynaptic partners. Keywords: Synapse, Neuron, Release probability, Action potential and Neuronal encoding

Introduction from presynaptic terminals [14-24], as well as by the num- In the neuronal networks, the information flows in a se- ber and responsiveness of postsynaptic receptors [25]. A quence of action potentials, synaptic transmission and study revealed an essential role of synaptic patterns affected action potentials [1,2]. The digital spikes and analogue by postsynaptic receptors in spike encodings [12]. It synaptic responses constitute the brain codes for well- remains unclear how these presynaptic factors regulate the organized behaviors and cognition. The conversions of dynamics of individual synapses , the signal integration from digital-to-analogue and analogue-to-digital signals are numerous synapses and the encoding of digital spikes at fulfilled by the interactions of the synapses and neurons postsynaptic neurons. Here, we present our study how glu- [3-13]. In the processing of signal conversion, how pre- tamate release probability regulates synapse dynamics and synaptic sequential spikes influence synapse dynamics neuron encoding in a preparation from cortical pyramidal and in turn regulate postsynaptic spike encoding neurons to GABAergic neurons. remains to be addressed in a quantitative manner. The revelation of these regulations helps understanding how numerous synapses are convergent onto each neuron Results and drive it to encode digital spikes precisely.  Information flow in neural network is a sequence of ac- The quantitative values of synapse dynamics are influ-  tion potentials at presynaptic neurons, signal transmis- enced by the probability of transmitter release, the number  sion at synapses and action potentials at postsynaptic of release sites and the content of released transmitters  cells, i.e., sequential conversions of digital-to-analogue and analogue-to-digital signals. In the analyses of their *Corresp y on L d a e b n f c o e r : B j r h a w in @i a b n p d .a C c. o c g n nitiveSciences,InstituteofBiophysics, h quantitativecorrelation,wefocusedoninvestigating 1 State Ke ow presynaptic sequential spikes influenced synapse Chinese Academy of Sciences, Beijing, China100101 dynamics, such as glutamate release probability and 2 Graduate School of Chinese Academy of Sciences, Beijing, China100049 © 2012 Yu et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.