Foreword * Contributors * Overview by Ari Sitaramayya * Cell Surface Receptors: Mechanisms of Signaling and Inactivation * Heterotrimeric G-proteins: Structure, Regulation and Signaling Mechanisms * Ras and Rho-Related Small Molecular Weight G-proteins: Structure and Signaling Mechanisms * Cyclic Nucleotides: Synthesis by Adenylyl and Guanylyl Cyclases * Phospholipases: Generation of Lipid-Derived Second Messengers * Cyclic Nucleotide Phosphodiesterases: Structure and Functional Aspects * Nitric Oxide: Synthesis and Intracellular Actions * Ionic Channels Mediating Sensory Transduction * Bits for an Organic Microprocessor: Protein Phosphorylation/Dephosphorylation * Defects in Signal Transduction Proteins Leading to Disease * Intracellular Messengers in Drug Addiction * Keyword Index