Journal of Neuroscience, Vol 10, 3335-3343, Copyright © 1990 by Society for Neuroscience
Excitation of locus coeruleus neurons by vasoactive intestinal peptide: role of a cAMP and protein kinase A
YY Wang and GK Aghajanian
Department of Pharmacology, School of Medicine, Yale University, New Haven, Connecticut.
In accord with previous studies, it was found that vasoactive intestinal
peptide (VIP), a powerful activator of adenylate cyclase, and cAMP-active
agents (i.e., 8-Br-cAMP, forskolin, and Ro20-1724) increased the firing
rate of noradrenergic neurons in the locus coeruleus (LC) by inducing an
inward current. The response to VIP was usually more rapid and larger in a
subpopulation of LC neurons with subthreshold rhythmic oscillations in
membrane potential (oscillatory cells) as compared to nonoscillatory cells.
In either case, the inward currents elicited by VIP and cAMP-active agents
were found to be nonadditive, suggesting the action of VIP, at least in
part, is via the same mechanism as that of cAMP-active agents.
Intracellular application of a specific protein (or related peptide)
inhibitor of cAMP-dependent protein kinase markedly attenuated the
activation induced by either cAMP-active agents or VIP, suggesting that
cAMP-dependent protein kinase (protein kinase A), presumably through
protein phosphorylation, plays a role in the action of VIP. Taken together,
the results provide evidence that cAMP and protein kinase A are involved in
mediating the electrophysiological actions of VIP on LC neurons.