The vascular beds of various cranial tissues receive common carotid flow, which contributes to blood flow redistribution associated with animal behaviors such as grooming, but the medullary autonomic regulation of carotid flow resistance (CAR) is poorly understood. This study is the first to examine the response sites of CAR in the rat rostral ventrolateral medulla (RVLM) presympathetic area to chemical stimulation by the ionotropic excitatory amino acid receptors activator L-cysteine. Arterial blood pressure and CAR were monitored in anesthetized rats which had a cranial window constructed above the ventral medulla. Mapping of L-cysteine microinjection in eight rats showed carotid vasoconstriction in the caudal part alone within the RVLM pressor area, which included contributions from other vascular beds, indicating localized topographic carotid vasoconstriction. Additional testing was performed on four types of denervated rats. A similar response map was obtained in six rats that received minimal lesions during surgery as well as in 10 rats with severed internal or external carotid nerves. However, the remaining three minimally lesioned rats showed extensive vasoconstriction of the RVLM pressor area including the rostral part, indicating lack of a topographic response. The topographic response of most rats might be state-dependent. Seven rats with complete cervical denervation showed no carotid vasoconstrictor response in the RVLM pressor area, indicating cervical sympathetic mediation of the responses. The topographic carotid vasoconstriction in response to L-cysteine may suggest differential roles of presympathetic neurons in the rostral and caudal parts of the RVLM in sympathetic carotid flow regulation.

中文翻译：

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大鼠延髓头侧腹外侧的地形图颈动脉血管收缩

各种颅骨组织的血管床接受共同的颈动脉血流，这有助于与动物行为（如梳理）相关的血流重新分配，但对颈动脉血流阻力 (CAR) 的髓质自主调节知之甚少。这项研究是第一个检查大鼠延髓腹外侧 (RVLM) 前交感神经区域中 CAR 对离子性兴奋性氨基酸受体激活剂 L-半胱氨酸化学刺激的反应位点的研究。在具有在腹侧髓质上方构建的颅窗的麻醉大鼠中监测动脉血压和CAR。L-半胱氨酸显微注射在 8 只大鼠中的映射显示 RVLM 升压区域内仅尾部部分的颈动脉血管收缩，其中包括来自其他血管床的贡献，表明局部地形颈动脉血管收缩。对四种类型的去神经大鼠进行了额外的测试。在 6 只在手术过程中受到最小损伤的大鼠以及 10 只具有颈内或颈外神经切断的大鼠中获得了类似的反应图。然而，其余三只损伤最小的大鼠表现出包括嘴部在内的 RVLM 升压区的广泛血管收缩，表明缺乏地形反应。大多数大鼠的地形反应可能与状态有关。7 只颈椎完全去神经支配的大鼠在 RVLM 升压区没有表现出颈动脉收缩反应，表明颈交感神经介导了这些反应。