Conivaptan, a Selective Arginine Vasopressin V_1a and V₂ Receptor Antagonist Attenuates Global Cerebral Edema Following Experimental Cardiac Arrest via Perivascular Pool of Aquaporin-4

Background: Cerebral edema is a major cause of mortality following cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). Arginine vasopressin (AVP) and water channel aquaporin-4 (AQP4) have been implicated in the pathogenesis of CA-evoked cerebral edema. In this study, we examined if conivaptan, a V_1a and V₂ antagonist, attenuates cerebral edema following CA/CPR in wild type (WT) mice as well as mice with targeted disruption of the gene encoding α-syntrophin (α-syn^−/−) that demonstrate diminished perivascular AQP4 pool. Methods: Isoflurane-anesthetized adult male WT C57Bl/6 and α-syn^−/− mice were subjected to 8 min CA/CPR and treated with either bolus IV injection (0.15 or 0.3 mg/kg) followed by continuous infusion of conivaptan (0.15 mg/kg/day or 0.3 mg/kg/day), or vehicle infusion for 48 h. Serum osmolality, regional brain water content, and blood–brain barrier (BBB) disruption were determined at the end of the experiment. Sham-operated mice in both strains served as controls. Results: Treatment with conivaptan elevated serum osmolality in a dose-dependent manner. In WT mice, conivaptan at 0.3 mg dose significantly attenuated regional water content in the caudoputamen (81.0 ± 0.5 vs 82.5 ± 0.4 % in controls; mean ± SEM) and cortex (78.8 ± 0.2 vs 79.4 ± 0.2 % in controls), while conivaptan at 0.15 mg was not effective. In α-syn^−/− mice, conivaptan at 0.3 mg dose did not attenuate water content compared with controls. Conivaptan (0.3 mg/kg/day) attenuated post-CA BBB disruption at 48 h in WT mice but not in α-syn^−/− mice. Conclusions: Continuous IV infusion of conivaptan attenuates cerebral edema and BBB disruption following CA. These effects of conivaptan that are dependent on the presence of perivascular pool of AQP4 appear be mediated via its dual effect on V₁ and V₂ receptors.