Ethanol microinjection into the area postrema selectively attenuates baroreflex sensitivity measured by vasopressin in conscious rats

Abstract

Microinjection of ethanol (10 μg) into the area postrema (AP) of conscious rats attenuated baroreflex sensitivity (BRS) measured by arginine vasopressin (AVP) (−1.73 ± 0.13 versus −2.47 ± 0.16 bpm/mmHg), but not by phenylephrine (PE) (−1.94 ± 0.26 versus −1.82 ± 0.20 bpm/mmHg). Intra-AP injection of the V 1 receptor antagonist n(CH 2) 5Tyr(Me)AVP replicated the differential effects of ethanol on BRS measured by AVP (−1.89 ± 0.11 versus −2.52 ± 0.10 bpm/mmHg) and PE (−2.10 ± 0.12 versus −2.09 ± 0.19 bpm/ mmHg). Intra-AP artificial cerebrospinal fluid (ACSF) did not change BRS measured by AVP or PE. These data suggest that ethanol attenuates the facilitatory action of AVP on baroreflexes via its interaction with AVP neurons in the AP.