Centrally administered interleukin-1 beta sensitizes to the central pressor action of angiotensin II

The objective of the present study was to find out whether brain vasopressin (AVP) and angiotensin II (Ang II) are involved in pressor response to intracerebroventricular (ICV) infusion of interleukin-1 beta (IL-1β). The experiments were performed on conscious, 12- to 14-week-old Sprague–Dawley rats. Mean arterial blood pressure (MAP) and heart rate (HR) were recorded continuously under baseline conditions and during ICV infusion periods. In the first part of the study, the rats were ICV-infused with one of the following: 0.9% NaCl saline (5 μl/h—control), IL-1β (100 ng/h), angiotensin AT1 receptor antagonist (losartan 10 μg/h), IL-1β together with losartan, V1 receptors antagonist (V1ANT), d(CH2)5[Tyr(Me)2,Ala-NH29]AVP, 400 ng/h) or IL-1β together with V1ANT. Saline infusion did not influence MAP, while administration of IL-1β elicited a significant but transient increase in MAP. The pressor response to IL-1β was abolished by losartan but not by V1ANT. On the other hand, combined administration of IL-1β and V1ANT resulted in increase in HR, which was absent during infusion of IL-1β alone. In the second part of the study after ICV pretreatment with IL-1β or 0.9% NaCl (control), the rats received ICV infusion of one of the following: 0.9% NaCl saline, subpressor dose of Ang II (5 ng/15 s) or subpressor dose of AVP (5 ng/15 s). Subpressor doses of Ang II and AVP did not influence MAP and HR in saline-pretreated rats. The same dose of Ang II but not AVP applied in IL-1β-pretreated rats resulted in a significant increase in MAP. The study provides evidence that IL-1β through its action in the brain increases sensitivity to central pressor action of Ang II. Additionally, we found that AVP and in particular V1 receptors do not play important role in the central pressor action of IL-1β, however, they may influence its effect on HR regulation.