The cardiovascular responses after lipopolysaccharide microinjection into the dorsomedial periaqueductal gray in rats

Introduction: The dorsomedial periaqueductal gray (dmPAG) is located around the cerebral aqueduct with various functions such as cardiovascular regulation and is affected by inflammation. Lipopolysaccharide (LPS) is a complex molecule with an inflammatory effect that is known to affect blood pressure. In the present study, the cardiovascular effect of LPS microinjection into the dmPAG was investigated. Methods: Rats were divided into three groups consisting of 1: control; 2: 50 ng LPS and 3: 100 ng LPS. Rats were mounted on a stereotaxic device after anesthesia and a continuous recording of cardiovascular parameters was done by a PowerLab device, connected to a cannulated femoral artery and drugs microinjected into dmPAG. The changes (∆) in systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP) and heart rate (HR) were calculated at different times and compared to the control group. Results: Both doses of LPS when microinjected into the dmPAG brought on a significant hypotensive response in the pressure parameters (MAP, SBP, and DBP) when compared to control. A non-significant increase in HR was also documented in both groups. Conclusion: The results of this experiment indicated that LPS, when microinjected into the dmPAG, induced a hypotensive response in anesthetized rats in both doses in comparison to control.