Time-Dependent Effects of Arginine-Vasopressin V1 Receptor Inhibition on Secondary Brain Damage after Traumatic Brain Injury.

Arginine-vasopressin (AVP) V1 receptors are known to mediate brain edema formation after traumatic brain injury (TBI). So far, however, AVP V1 receptors were only inhibited by genetic deletion or prior to trauma. Therefore, the current study aimed to determine the therapeutic window of AVP V1 receptor antagonization after TBI. Male C57BL/6 mice (n = 7 per group) were subjected to controlled cortical impact (CCI), and 500 ng of a selective peptide V1 receptor antagonist (V1880) were applied by intracerebroventricular injection 5 min, and 1, 3, and 6 h thereafter. After 24 h, brain water content (BWC), intracranial pressure (ICP), and secondary contusion expansion volume were assessed. Neurological function was assessed daily for 7 days after trauma. Inhibition of AVP V1 receptors within 1 h after TBI significantly reduced BWC from 81.6 ± 0.7 to 80.6 ± 0.7% (mean ± SD; p < 0.05). Reduction of brain edema resulted in a significant decrease in ICP from 25.9 ± 1.8 mm Hg to 21.0 ± 1.5 mm Hg (p < 0.05) and a reduction in contusion volume (26.1 ± 2.5 mm3 vs. 30.1 ± 2.0 mm3 in controls; p < 0.05). This reduction of brain injury resulted in a significantly improved neurological function 7 days after trauma. Treatments initiated 6 h after TBI had no effect. The results of the current study demonstrate that inhibition of AVP V1 receptors improve outcome after experimental TBI when given within a clinically relevant time window. Therefore, AVP V1 receptors may represent a therapeutic target with clinical potential.