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. www.phypha.ir/ppjOriginal Article Physiology and Pharmacology 25 (2021) 334-340The periaqueductal gray (PAG) is located around the cerebral aqueduct of the brain and is involved in numerous functions such as stress, defensive reactions and cardiovascular regulation (Bandler and Shipley, 1994).The PAG has connections to several parts of the brain and is functionally divided into four subdivisions: dlPAG, dmPAG, lPAG and the vlPAG.Although the roles of the dlPAG and the vlPAG subdivisions have been documented in previous studies, such as the hypertensive effect of nitric oxide in the dlPAG (Abadi et al., 2020) or the hypotensive effect of excitatory amino acids in the vlPAG (Keay et al., 1997), few have been done on the dmPAG.The dmPAG receive inputs