3',5'-cyclic adenosine monophosphate regulates expression of synaptotagmin in neonatal sympathetic ganglia in vitro.

The expression of the synaptic vesicle protein, synaptotagmin, in developing rat superior cervical ganglia is influenced by transsynaptic factors associated with membrane depolarization. The present study examines the role of cyclic AMP in the regulation of synaptotagmin in neonatal superior cervical ganglia maintained in explant culture. Ganglia were treated for 48 h in vitro with the Na+-channel ionophore, veratridine, or with pharmacological agents that alter cyclic AMP levels. Levels of cyclic AMP and synaptotagmin were determined by radioimmunoassay. Veratridine treatment significantly increased cyclic AMP in cultured ganglia, with a long time course, and also increased synaptotagmin levels. Drugs that elevate cyclic AMP levels significantly increased synaptotagmin levels, with similar magnitude to that produced by veratridine treatment. These pharmacological agents did not alter neuron survival or total ganglionic protein content. No additive effects were observed after combined treatment with veratridine and pharmacological agents that increased cyclic AMP. Agents that blocked adenylyl cyclase blocked the veratridine-induced increase in synaptotagmin levels. The results suggest that regulation of expression of synaptotagmin in neonatal sympathetic neurons is mediated partially by cyclic AMP.