Vasopressin Protects Hippocampal Neurones in Culture Against Nutrient Deprivation or Glutamate-Induced Apoptosis

Vasopressin (VP) secreted within the brain modulates neuronal function by acting as a neurotransmitter. Recent studies show that VP prevents serum deprivation-induced apoptosis in the neuronal cell line, H32. To determine whether VP is anti-apoptotic in hippocampal neurones, primary cultures of these neurones were used to examine the effect of VP on neuronal culture supplement (B27) deprivation-, or glutamate-induced apoptosis, and the signalling pathways mediating the effects. Removal of B27 supplement from the culture medium for 24 h or the addition of glutamate (3-10 mu m) decreased neuronal viability (P < 0.05) and increased Tdt-mediated dUTP nick-end labelling (TUNEL) staining and caspase-3 activity (P < 0.05), which is consistent with apoptotic cell death. VP (10 nm) reduced B27 deprivation- or glutamate-induced cell death (P < 0.05). These anti-apoptotic effects of VP were completely blocked by a V1 but not a V2 receptor antagonist, indicating that they are mediated via V1 VP receptors. The anti-apoptotic effect of VP in neurones involves activation of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) and inositol trisphosphate/protein kinase B (Akt) signalling pathways. This was shown by the transient increases in phospho-ERK and phospho-Akt after incubation with VP revealed by western blot analyses, and the ability of specific inhibitors to reduce the inhibitory effect of VP on caspase-3 activity and TUNEL staining by 70% and 35%, respectively (P < 0.05). These studies demonstrate that VP has anti-apoptotic actions in hippocampal neurones, an effect that is mediated by the MAPK/ERK and phosphatidylinositol-3 kinase/Akt signalling pathways. The ability of VP to reduce nutrient deprivation or glutamate overstimulation-induced neuronal death suggests that VP acts as a neuroprotective agent within the brain.