Chapter 21 The function of A2 adenosine receptors in the mammalian brain: Evidence for inhibition vs. enhancement of voltage gated calcium channels and neurotransmitter release

Abstract

This chapter discusses the results in the context of previous reports on the role of A 2 receptors in synaptic transmission in the mammalian brain, and concludes that there are few cases in which A 2 receptors have been shown to be excitatory in directly increasing the release of a specific central nervous system (CNS) neurotransmitter. Although in several studies the overall effect of the activation of A 2 receptors has been to increase network excitability, most of these results would be compatible with an indirect effect through inhibition of γ-aminobutyric acid (GABA) release. GABA release tends to be inhibited by activation of A 2 receptors that would be consistent with the inhibition of N- and L-type calcium channels and also with the frequent observation of increased excitability of neuronal networks. Activation of A 2 receptors has been shown to result in inhibition of both calcium channels and GABAergic transmission. Presumably, the localization of A 2 receptors on GABAergic terminals results in inhibition of calcium channels and inhibition of GABA release.