Changes in immunoreactive vasopressin concentrations in brain regions of the rat in response to endotoxin

The purpose of this investigation was to examine the changes in brain vasopressin (AVP) concentrations induced by endotoxin in the rat. Thirteen areas of the brain and the plasma were extracted and assayed for AVP under control conditions and at two times after endotoxin, 60 min (hypothermic phase) and 330 min (hyperthermic phase). There were no changes in AVP concentrations in the neurohypophysis, median eminence, supraoptic nucleus, paraventricular nucleus, suprachiasmatic nucleus, hippocampus or brainstem (nucleus of solitary tract). Decreased concentrations occurred at 330 min post-endotoxin in the lateral septum, medial septum, amygdala and caudate whereas increases occurred in the preoptic/anterior hypothalamus and cerebellum. Plasma levels increased by 60 min post-endotoxin and were still elevated by 330 min post-endotoxin. Endotoxin induces changes in AVP concentrations in several areas of brain, which may reflect alterations in turnover, perhaps related to the febrile rise in body temperature.