Long-term increases in neurotransmitter release from neuronal cells expressing a constitutively active adenylate...

Signal-transduction pathways mediate a wide range of short-term changes in the physiology of neuronal systems from invertebrates to mammals. However, examples of long-term changes in neuronal physiology mediated by these pathways have been limited to invertebrate systems. In this report, long-term changes in the physiology of mammalian neurons were studied by using genetic intervention to cause a long-lasting activation of the cAMP pathway. The catalytic domain of yeast adenylate cyclase (cyr), encoding a constitutive enzyme activity, was expressed in neuronal cells infected with a defective herpes simplex virus vector (pHSVcyr). In PC-12 cells infected with pHSVcyr, increases were seen in cAMP levels, protein kinase A activity, protein phosphorylation, phosphorylation of the tyrosine hydroxylase protein kinase A site (Ser40), and catecholamine release. Infection of sympathetic neurons with pHSVcyr increased cAMP levels, protein phosphorylation, and catecholamine release. Yeast adenylate cyclase immunoreactivity and elevated cAMP levels were localized to the cell bodies of sympathetic neurons. The increase in neurotransmitter release was both Ca(2+)- and activity-dependent and persisted for at least 1 week after infection of the sympathetic neurons, suggesting that sustained physiological activation of the cAMP pathway may mediate long-term changes in the neuronal physiology of mammalian systems.