Ghorbani Atiyeh, Mohebbati Reza, Rahimi Alireza, Alikhani Vida, Shafei Mohammad Naser
Department of Physiology, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.
Applied Biomedical Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
Iran J Basic Med Sci. 2023;26(8):891-898. doi: 10.22038/IJBMS.2023.66838.14660.
Due to the presence of the cholinergic system in the lateral periaqueductal gray (lPAG) column, the cardiovascular effects of acetylcholine (ACH) and its receptors in normotensive and hydralazine (HYD) hypotensive rats in this area were evaluated.
After anesthesia, the femoral artery was cannulated and systolic blood pressure (SBP), mean arterial pressure (MAP), heart rate (HR), and also electrocardiogram for evaluation of low frequency (LF) and high frequency (HF) bands, important components of heart rate variability (HRV), were recorded. ACH, atropine (Atr, a muscarinic antagonist), and hexamethonium (Hex, an antagonist nicotinic) alone and together microinjected into lPAG, changes (Δ) of cardiovascular responses and normalized (n) LF, HF, and LF/HF ratio were analyzed.
In normotensive rats, ACH decreased SBP and MAP, and enhanced HR while Atr and Hex did had no effects. In co-injection of Atr and Hex with ACH, only ACH+Atr significantly attenuated parameters. In HYD hypotension, ACH had no affect but Atr and Hex significantly improved the hypotensive effect. Co-injection of Atr and Hex with ACH decreased the hypotensive effect but the effect of Atr+ACH was higher. In normotensive rats, ACH decreased nLF, nHF, and nLF/nHF ratio. These parameters in the Atr +ACH group were significantly higher than in ACH group. In HYD hypotension nLF and nLF/nHF ratio increased which was attenuated by ACH. Also, Atr+ACH decreased nLF and nLF/nHF ratio and increased nHF.
The cholinergic system of lPAG mainly via muscarinic receptors has an inhibitory effect on the cardiovascular system. Based on HRV assessment, peripheral cardiovascular effects are mostly mediated by the parasympathetic system.
由于导水管周围灰质外侧柱（lPAG）中存在胆碱能系统，因此评估了乙酰胆碱（ACH）及其受体对正常血压和肼屈嗪（HYD）诱导的低血压大鼠该区域心血管系统的影响。
麻醉后，插入股动脉导管，记录收缩压（SBP）、平均动脉压（MAP）、心率（HR），并记录心电图以评估心率变异性（HRV）的重要组成部分低频（LF）和高频（HF）波段。单独及联合将ACH、阿托品（Atr，一种毒蕈碱拮抗剂）和六甲铵（Hex，一种烟碱拮抗剂）微量注射到lPAG中，分析心血管反应的变化（Δ）以及标准化的（n）LF、HF和LF/HF比值。
在正常血压大鼠中，ACH降低SBP和MAP，并提高HR，而Atr和Hex无此作用。Atr和Hex与ACH联合注射时，只有ACH + Atr能显著减弱各项参数。在HYD诱导的低血压大鼠中，ACH无影响，但Atr和Hex能显著改善低血压效应。Atr和Hex与ACH联合注射可降低低血压效应，但Atr + ACH的作用更强。在正常血压大鼠中，ACH降低nLF、nHF和nLF/nHF比值。Atr + ACH组的这些参数显著高于ACH组。在HYD诱导的低血压大鼠中，nLF和nLF/nHF比值升高，ACH可使其减弱。此外，Atr + ACH降低nLF和nLF/nHF比值，并升高nHF。
lPAG的胆碱能系统主要通过毒蕈碱受体对心血管系统产生抑制作用。基于HRV评估，外周心血管效应主要由副交感神经系统介导。
