No abstract

The present study was designed to determine the role of centrally acting oxytocin (OT) in the regulation of blood pressure during chronic mild stress (CMS) in spontaneously hypertensive (SHR; n = 36) and normotensive Wistar-Kyoto (WKY; n = 38) rats. The rats were implanted with osmotic minipumps for intracerebroventricular infusions of 0.9% NaCl, OT, and oxytocin receptor antagonist (OTANT) and divided into two groups: SHR and WKY 1) exposed to 4-wk CMS and 2) not exposed to stress (controls). After 4 wk, hemodynamic parameters were recorded at rest and after an application of acute stressor [air-jet stress (AJS)]. Resting mean arterial blood pressure (MAP) was significantly lower in CMS-exposed SHR and WKY infused with OT than in the corresponding groups receiving saline. Exposure to CMS exaggerated the AJS-dependent pressor response in WKY receiving saline but not in the corresponding group of SHR. OT infusion reduced the AJS-dependent pressor response in both CMS-exposed and not exposed SHR and in CMS-exposed WKY. Intracerebroventricular infusion of OTANT potentiated the AJS-dependent pressor response in both stressed and not stressed WKY rats but not in SHR. The results show that centrally delivered OT decreases resting MAP during CMS in both SHR and WKY rats and that in SHR it reduces pressor responses to AJS under control and CMS conditions, whereas in WKY this effect is significant only after CMS exposure. The study indicates that endogenous centrally acting OT may play an essential role in buffering pressor responses to AJS in CMS-exposed and not exposed WKY rats and that this function is significantly impaired in SHR.

No abstract

A high‐fat diet can affect the central activity of the apelinergic and vasopressinergic systems, which can have a significant impact on cardiovascular regulation. The aim of the study was to investigate the role of the central interaction between apelin and vasopressin in the regulation of the cardiovascular system in Sprague Dawley rats maintained on a normal‐fat diet (NFD) or on a high‐fat diet (HFD). The animals were instrumented with a cannula implanted into the left cerebral ventricle for intracerebroventricular (ICV) infusions of saline (0.9% NaCl), apelin‐13 (APLN‐13), V1a receptor antagonist (V1aRANT) APJ receptor antagonist (F13A), vasopressin (AVP); and with a catheter placed within the femoral artery for mean arterial blood pressure and heart rate monitoring. Blood, the hypothalamus and the medulla oblongata were collected for biochemical analysis. The hypertensive effect of APLN‐13 was blocked by a prior ICV infusion of V1aRANT, only in the NFD rats. However, the hypertensive effect of AVP was blocked by the prior ICV infusion of F13A in both the NFD and HFD rats. A HFD caused an increase in the protein level of APJ and V1a receptors, both in the hypothalamus and the medulla oblongata. This study confirms the presence of an interaction between both peptides in the central regulation of the cardiovascular system in rats on a NFD or a HFD.

No abstract