Regulation of Arginine-vasopressin (AVP)

Evidence suggests that altered N-methyl-D-aspartate (NMDA) receptor activity and glutamate signaling may underlie the pathogenesis of both schizophrenia and depression at least in subgroups of patients. In schizophrenia, pharmacologic modeling, postmortem and imaging data suggest reduced NMDA signaling. In contrast, recent clinical trials demonstrating the efficacy of the NMDA antagonist ketamine in severely depressed patients suggest increased NMDA receptor signaling. The Investigators have conducted a proof of concept study to assess whether there is any in vivo evidence for an inverse association in depression and schizophrenia with respect to the NMDA receptor function. For this purpose the investigators used a translational approach, based on findings from animal studies that NMDA receptor is a key mediator of arginine-vasopressin (AVP) release into the bloodstream. Using hypertonic saline to induce AVP release, as done in animal studies, it was found that in a subgroup of depressed patients, NMDA receptor mediated AVP release was significantly increased, whereas in a subgroup of schizophrenia patients, the same response was abnormally low. Previous research has demonstrated that this response is well conserved. These findings are consistent with implicated NMDA receptor related abnormalities in depression and schizophrenia in subgroups of patients, and provide the first in vivo evidence towards this dichotomy.