Effect of aortic baroreceptor deafferentation on plasma vasopressin and oxytocin in the conscious rat

Abstract

Experiments were done in conscious, unrestrained rats to investigate the effects of selective aortic baroreceptor deafferentation (ABD) on circulating levels of the neurohypophysial hormones arginine vasopressin (AVP) and oxytocin (OXY). Plasma concentration of AVP and OXY were measured by radioimmunoassay before and 1–13 days after cutting the aortic depressor nerves, bilaterally. Arterial pressure was significantly elevated by approximately 12–39 mmHg above control levels after ABD. On day one after ABD, plasma AVP increased from control levels of 3.21 ± 1.56 pg/ml to 8.29 ± 4.66 pg/ml (258%) and plasma OXY increased from 2.53 ± 4.24 pg/ml to 8.16 ± 1.49 pg/ml (323%). However, by the third day after ABD, plasma AVP and OXY levels had returned to pre-ABD control levels. On days 8 and 13 after ABD, AVP levels were elevated again by approximately 2- and 9-fold, respectively, whereas the OXY levels remained at control levels. These data suggest that in the awake rat, the release of AVP and OXY is modulated differentially after ABD and that the increased circulating levels of AVP may be one of the mechanisms that contributes to the elevated arterial pressure in neurogenic hypertension.