McAfee D A, Schorderet M, Greengard P
Science. 1971 Mar 19;171(3976):1156-8. doi: 10.1126/science.171.3976.1156.
Brief periods of stimulation of the preganglionic nerve fibers produced a severalfold increase in the content of adenosine 3',5'-monophosphate in superior cervical sympathetic ganglia, whereas postganglionic stimulation did not. These and other experiments indicated that the increased concentrations of adenosine 3'5'-monophosphate were closely associated with the process of synaptic transmission. This increase occurred primarily in postsynaptic cells.