However, BDNF when injected alone had no appreciable effect when compared to PBS injections, and enhanced the effect of rSCs transplantation. We figure that BDNF combined cell transplantation could get a better vision function restoration at first month after transplantation because of BDNF can help graft cells get a better survival rate. Or may be BDNF related signal pathway participate into synapse formation and host retina circuitry. In future, more work has to be done on this hypothesis.

Although rSCs+BDNF and rSCs transplants show a better maintenance of the ERG and ONL thickness than PBS and BDNF injections over the first two months albeit diminished, the enhancement due to rSCs+BDNF transplants was only apparent in the first month after the operation. We suggest that effects of the BDNF are limited due to diminished concentration of BDNF following transplantation. In the future, we will give the recipients multiple injections of exogenous BDNF to determine if a maintained concentration of BDNF is required to prolong the beneficial effects of rSCs transplantation.

Acknowledgments Supported by National Basic Research Program of China Grants 2007CB512203 and 2005CB724302 and by Nature Science Foundation of China Grant 30772371. The authors thank Dr. T. FitzGibbon for comments on earlier drafts of the manuscript and Ms. Yu Xiao Zeng for excellent technical support.

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Chapter 44

The Role of Purinergic Receptors in Retinal

Function and Disease

Michelle M. Ward, Theresa Puthussery, Kirstan A. Vessey, and Erica L. Fletcher

Abstract Extracellular ATP acts as a neurotransmitter in the central and peripheral nervous systems. In this review, the role of purinergic receptors in neuronal signaling and bi-directional glial-neuronal communication in the retina will be considered. There is growing evidence that a range of P2X and P2Y receptors are expressed on most classes of retinal neurons and that activation of P2 receptors modulates retinal function. Furthermore, neuronal control of glial function is achieved through neuronal release of ATP and activation of P2Y receptors expressed by Müller cells. Altered purinergic signaling in Müller cells has been implicated in gliotic changes in the diseased retina and furthermore, elevations in extracellular ATP may lead to apoptosis of retinal neurons.

44.1 Introduction

Extracellular ATP and other nucleotides are now recognized neurotransmitters that act in the peripheral and central nervous systems to facilitate neurotransmission and neuromodulation, and are also involved in developmental and disease processes (Abbracchio et al. 2008). In the following review, the role of purinergic receptors in retinal function and disease will be explored.

Two families of receptors respond to ATP and its degradation products; P1 receptors are solely activated by adenosine and P2 receptors (P2R) respond to extracellular nucleotides including ATP. The P2 receptor family can be further subdivided by the intracellular signaling pathway of the receptor. P2X receptors belong to the ionotropic class of receptors whilst P2Y receptors are members of the metabotropic receptor family. There are currently seven known subtypes of P2X receptor (P2X1–7) and eight subtypes of P2Y receptors (P2Y1, 2, 4, 6, 11, 12, 13, and 14;

M.M. Ward (B)

Department of Anatomy and Cell Biology, The University of Melbourne, Grattan St, Parkville 3010, Victoria, Australia

e-mail: m.ward@unimelb.edu.au

Medicine and Biology 664, DOI 10.1007/978-1-4419-1399-9_44,C Springer Science+Business Media, LLC 2010