Journal of Neuroscience, Vol 9, 752-759, Copyright © 1989 by Society for Neuroscience
Vasopressin neuromodulation in the hippocampus
RE Brinton and BS McEwen
Laboratory of Neuroendocrinology, Rockefeller University, New York, New York 10021.
This study explored an effector mechanism associated with the arginine
vasopressin (AVP) recognition site in the hippocampus, namely, potentiation
of norepinephrine (NE)-induced cAMP accumulation in the surviving
hippocampal slice. The biochemical mechanisms that underlie the AVP
potentiation were investigated as follows: First, the actions of AVP upon
NE-induced accumulation of cAMP in hippocampal slices from rat brain were
specific to AVP and not shared by other closely related peptides, namely,
oxytocin and AVP4-9. Second, the AVP-induced neuromodulation involved
beta-adrenergic receptors, with AVP having no effect on cAMP levels in the
absence of NE. Third, the potentiation by AVP was biphasic, with lower AVP
concentrations potentiating NE-induced cAMP accumulation, while higher
concentrations did not potentiate. Fourth, an antagonist of V1-type AVP
receptors blocked AVP potentiation. Fifth, AVP potentiation was dependent
upon extracellular calcium concentrations. Sixth, AVP potentiation was
blocked by 50 microM trifluoperazine, which is consistent with a
calcium-calmodulin involvement but which might also implicate protein
kinase C. These alternatives and the nature of the calcium involvement are
discussed. AVP actions thus appear to involve interactions between several
second- messenger systems and suggest a biochemical mechanism by which AVP
exerts its centrally mediated behavioral effects.