Cardiovascular Effect of Dorsal Periaqueductal Gray During Lipopolysaccharide-induced Hypotension

The central mechanism related to the cardiovascular response to lipopolysaccharide (LPS)-induced hypotension is not entirely known, but it is suggested that numerous brain areas such as dorsal periaqueductal gray (dPAG) are involved in this process. In the current work, the cardiovascular effect of the dPAG during LPS-induced hypotension is investigated.

The study animals (rats) were divided into four groups: control (saline microinjected into dPAG), lidocaine 2%, LPS (intravenously injected), and lidocaine + LPS. Catheterization of the femoral artery and vein was performed to record blood pressure and LPS injection, respectively. Saline and lidocaine were microinjected into the dPAG nucleus then the LPS injection was performed. The changes (∆) in systolic blood pressure (SBP), mean arterial pressure (MAP), and heart rate (HR) were measured and compared with those of the control and LPS groups.

LPS significantly declined ∆MAP and ∆SBP (P<0.05) but did not change the ∆HR compared to the control. Lidocaine did not significantly affect basic ∆SBP, ∆MAP, and ∆HR compared to the control. Injection of lidocaine before LPS significantly attenuated the reduction of ∆SBP and ∆MAP evoked by LPS (P<0.05).

Our data showed that blockade of the dPAG by lidocaine significantly ameliorates the hypotension induced by LPS. this finding confirms the involvement of the dPAG in cardiovascular regulation during LPS-induced hypotension.