The Modulation of Synaptic Transmission by the Glial Purinergic System

Abstract: Accumulating evidence indicates that bioactive substances produced by glia play an important role in the modulation of synaptic transmission. Astrocytes and microglia express many types of P2 purinoceptors and the stimula-tion of these receptors causes the release of bioactive substances, termed “gliotransmitters”, such as ATP, glutamate and cytokines. Gliotransmitters are able to modulate synaptic transmission. In this article, the P2X 4 R and P2Y 12 R systems of microglia, which modulate the synaptic transmission between dorsal root ganglion neurons and dorsal horn neurons, are described. In addition, the role of the astrocyte purinergic system in synaptic transmission is discussed. The modulation of synaptic transmission by glial purinergic systems is a novel perspective on the regulation of brain and nerve function and is a new target for the development of medicines. Keywords: ATP receptors, microglia, astrocyte, synaptic transmission. 1. INTRODUCTION In 1972, Burnstock proposed new a role for nucleotides; that of neurotransmission [1]. Recently, numerous subtypes of ATP and adenosine receptor have been cloned, which has led to the acceptance of the “purinergic nervous system”. Now purinergic receptors are divided into two big families, P1 (receptors for adenosine and AMP) and P2 (receptors for nucleotides). Four subtypes of P1 receptors have been cloned, namely, A