The role of adenosine and its nucleotides in central synaptic transmission.

Less than two decades ago Sutherland and Rall (1958; Rall et al., 1957) discovered a heat stable factor now known as adenosine 3′,5′-monophosphate, which accumulated in particulate fractions of liver homogenates exposed to epinephrine. This factor activated the breakdown of glycogen by soluble cytoplasmic enzymes. Although epinephrine activates glycogenolysis in intact hepatocytes, the hormone has no such effect on the soluble enzymes. Sutherland and Rall (1960; Rall and Sutherland, 1958, 1961, 1962) proposed that epinephrine might trigger the glycogenolytic response of hepatocytes by activating the synthesis of this nucleotide (cyclic AMP) whose structure (Fig. 1) by then had been shown to contain a unique cyclic phosphate bond (Lipkin et al., 1959). The polypeptide hormone glucagon also triggers the glycogenolytic response of liver, and activates the synthesis of cyclic AMP. From these and related observations on the actions of other hormones, the concept arose that cyclic AMP functioned as an intracellular “second messenger”, synthesized in response to certain hormones and which, by activating the appropriate sequence of enzymes, produced the specific biologic response of the target cell to the hormone (Sutherland et al., 1965).

M. Phillips

Papers

Effects of therapeutic agents on cyclic AMP metabolism in vitro.