Reddy S V, Yaksh T L, Anderson R E, Sundt T M
Brain Res. 1986 Feb 19;365(2):278-88. doi: 10.1016/0006-8993(86)91639-2.
In pentobarbital-anesthetized cats, over arterial paCO2 values of 20-60 mm Hg, cerebral blood flow (CBF, Xenon) and cardiac output (CO, thermal dilution) show positively inflicted curves with slopes significantly greater than zero. To examine the role of the locus coeruleus (LC) in these responses, bilateral stereotactic thermo-coagulation lesions of the LC were made. The effect of lesions confirmed to involve the LC bilaterally (n = 10), were compared with the effects of misdirected lesions placed in the cerebellum and lateral to the LC (n = 10) and sham lesions (n = 10). Ten days after the lesioning procedure, the animals were re-anesthetized with pentobarbital and paCO2 response curves were determined for CBF and CO prior to and following intravenous administration of propranolol (1 mg/kg, i.v.). The results obtained with the sham-operated animals and the animals with lesions outside of the LC were indistinguishable. Bilateral LC lesions had no significant effect on normocapnic CBF as compared to control animals. They did, however, significantly reduce the slope of the CBF paCO2 response curve. Propranolol produced a significant reduction in CBF in lesioned and non-lesioned animals measured at all levels of pCO2 and did not alter the slope of the pCO2 response curve for any group as compared to predrug values. Bilateral lesions of the LC did not significantly alter either normocapnic CO or the slope of the CO-paCO2 relationship, but did reduce the elevation in mean arterial blood pressure otherwise observed during hypercarbia. Measurement of norepinephrine levels in cortex indicate a close correlation between the ability of the lesion to reduce norepinephrine content and produce the observed physiological effects. The results of these experiments suggest that the hypercapnic response of CBF, but not CO to arterial paCO2 is modulated by systems which traverse the dorsal brainstem. The role of the locus coeruleus-catecholamine cell bodies in this effect, however, must be considered speculative until further transmitter-selective interventions are carried out.
在戊巴比妥麻醉的猫中，动脉血二氧化碳分压（PaCO₂）值在20 - 60 mmHg范围内时，脑血流量（CBF，氙清除法）和心输出量（CO，热稀释法）呈现正相关曲线，其斜率显著大于零。为了研究蓝斑核（LC）在这些反应中的作用，对LC进行了双侧立体定向热凝损伤。将双侧损伤确认为累及LC的动物（n = 10）的效应，与放置在小脑和LC外侧的误定向损伤（n = 10）以及假损伤（n = 10）的效应进行比较。损伤操作十天后，用戊巴比妥再次麻醉动物，并在静脉注射普萘洛尔（1 mg/kg，静脉注射）之前和之后测定CBF和CO的PaCO₂反应曲线。假手术动物和LC以外有损伤的动物所获得的结果没有差异。与对照动物相比，双侧LC损伤对正常碳酸血症时的CBF没有显著影响。然而，它们确实显著降低了CBF - PaCO₂反应曲线的斜率。在所有pCO₂水平下，普萘洛尔使损伤和未损伤动物的CBF显著降低，并且与给药前值相比，未改变任何组的pCO₂反应曲线斜率。双侧LC损伤既没有显著改变正常碳酸血症时的CO，也没有改变CO - PaCO₂关系的斜率，但确实降低了高碳酸血症时原本观察到的平均动脉血压升高。皮质中去甲肾上腺素水平的测量表明，损伤降低去甲肾上腺素含量的能力与产生观察到的生理效应之间存在密切相关性。这些实验结果表明，CBF对动脉PaCO₂的高碳酸血症反应而非CO的反应，受到穿过脑桥背侧的系统的调节。然而，在进行进一步的递质选择性干预之前，蓝斑核 - 儿茶酚胺细胞体在这种效应中的作用必须被视为推测性的。
