Introduction The vertebrate central nervous system (CNS) is characterized by a dynamic interplay between signal transduction molecules and their cellular targets. Modulation of synaptic transmission by metabotropic or ionotropic receptors is an important source of control and dynamical adjustment in synaptic activity. Recent studies have provided new insights into the role of ligand-gated ion channels in modifying synaptic transmission. Along with a growing list of different types of pre- and postsynaptic ionotropic receptors and the cell types that express them, there have also been advances in characterizing the modulatory mechanisms of the receptors that link to receptor activation. This is important due to the convergence of data from biochemical, molecular, and electrophysiological studies, implicating ionotropic receptors in the effects of psychoactive and addictive drugs. 1 2 1 3 4 GPCR signaling is subject to extensive negative regulation through receptor desensitization, sequestration, and downregulation, termination of G protein activation by GTPase-activating proteins, and enzymatic degradation of second messengers. Additional protein-protein interactions positively modulate GPCR signaling by influencing ligand binding and specificity. 5 6 7 1 2A 2B 3 1 2A 8 1 9 10 1 11 1 2A 3 1 1 A + Functional interactions with metabotropic receptors g r a f s 12 13 \documentclass[12pt]{minimal}
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\begin{document}$$ {\text{G}}_{{\beta \chi }}  $$\end{document} + 1–4 2+ 2 2 \documentclass[12pt]{minimal}
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\begin{document}$$ {\text{G}}_{{{\alpha {\text{i}}} \mathord{\left/  {\vphantom {{\alpha {\text{i}}} 0}} \right.  \kern-\nulldelimiterspace} 0}}  $$\end{document} 14 15 1 2 16 18 1 19 20 1 3 3 21 22 29 3 30 31 2+ 2+ 32 33 3 1 34 3 1 3 1 1 35 1 3 3 36 3 3 1 37 3 3 1 3 3 3 1 1 3 1 2A 2A 2A 38 1 2A 39 1 2A 18 1 2A 1 2A 40 42 1 2A 1 2A 1 40 43 44 1 2A 16 17 45 47 2A 1 1 2A 2A 1 1 46 47 1 2A 18 2A 1 1 2A 16 48 1 2A 1 2A 2A 2A 49 1 2A 2A 18 Interactions between adenosine and dopaminergic system 1 2A 50 1 1 1 1 1 1 1 1 1 1 51 52 53 1 2 1 2 1 1 2A 2 54 53 2A 2A 55 1 1 1 5 6 1 5 56 58 59 + 2+ 60 1 61 1 1 1 62 1 1 1 35 36 1 1 1 1 Fig. 1 1 1 N 6 a 1 b n p # p  1 2 1 1 1 1 Fig. 2 1 N 6 1 1 n p # p  1 1 1 1 1 1 i/0 1 q 11 1 1 63 1 1 64 65 64 66 70 1 1 1 1 1 i/0 1 1 71 73 1 1 1 1 Functional interaction with ionotropic receptors + + 2+ − 74 + + 75 A 3 76 1 35 77 1 10 78 79 1 80 82 84 A 85 88 80 89 91 1 1 86 92 93 1 81 1 84 94 1 1 1 95 96 1 83 1 2A 1 83 1 2A 97 98 1 99 1 78 1 35 100 84 1 101 1 A A 102 A 1 1 85 85 86 1 87 88 86 1 A 2A 103 1 A 1 104 A 1 19 1 A 19 A 105 1 36 1 106 1 107 1 108 1 A 1 1 109 110 A 1 108 1 A A 1 A 1 111 1 A 1 1 7 63 112 113 1 6 2 4 4 6 91 7 114 7 80 89 115 116 38 90 117 118 1 118 1 119 1 120 + + ATP 121 122 1 1 ATP 123 1 ATP 124 125 ATP ATP 126 2A 127 1 ATP ATP 1 3 128 129 40 130 131 132 1 1 1 128 133 133 Concluding remarks 4 1 5 1 ATP 3 1 Fig. 3 1 1 2A 1 1 1 1 2A 1 2A 1 1  Fig. 4 1 1 2+ 1 ATP A  Fig. 5 1  There is evidence that various regulatory mechanisms exist as well as multiple mechanisms that act independently of each other on the same cell depending on the brain region and cell type. The overaction and redundancy principle ensures transmitter homeostasis under pathophysiological conditions in a special time window. The function of adenosine receptors in the regulation of the synaptic transmission is complex. 2A 1 ATP 80 1 1 134 1 1