Williams C A, Roberts J R, Freels D B
Department of Physiology, College of Medicine, East Tennessee State University, Johnson City 37614-0002.
Cardiovasc Res. 1990 Oct;24(10):821-33. doi: 10.1093/cvr/24.10.821.
The aim was to determine whether areas in the periaqueductal grey matter, medial dorsal raphe, or ventrolateral medulla might be involved with the integration of blood pressure and heart rate during isometric exercise.
Cats were anaesthetised with alpha chloralose (75 mg.kg-1) and catheters inserted into the right jugular vein and carotid artery. Isometric contractions were generated using a microprocessor controlled stimulator and sleeve electrode around the tibial nerve. Bilateral lesions were made in the dorsal periaqueductal grey matter (P1.0, LR2.0, HD + 1.5 mm) or two sites in the ventrolateral medulla (P12.0, RL 2.0, HD -10 mm; or P12.0, RL 2.0, HD -8.5 mm). Lesions were also made in the medial dorsal raphé nuclei (P1.0, RL 0.0, HD +1.5 mm). Clonidine was injected into the cerebral aqueduct to determine whether it would exert an antipressor effect during muscle contraction after the lesions were made. Only one site of lesion was made in a group of animals. Bilateral injections of clonidine (250 ng in 0.5 microliter) were made into the intact ventrolateral medulla (P11.5, RL 4.0, HD -8.5 mm) to explore its role further. Fatiguing contractions were performed before and after the lesions were made, or clonidine was injected, and changes in arterial blood pressure and heart rate were measured. Verification of the lesion sites or the microinjection sites, and the extent of the lesion or spread of the clonidine, was made from histological examination of brain tissue after each experiment.
Adult cats of either sex, n = 20, weight 2.4 (SD 0.4) kg, were used.
Fatiguing isometric contractions in control conditions caused mean arterial pressure to increase by 45-50 mm Hg and heart rates by 20-25 beats.min-1. Bilateral lesions in the dorsal periaqueductal grey matter did not alter resting mean arterial pressure but attenuated the pressor response during contractions. Injections of clonidine into the cerebral aqueduct had no further antipressor effects after the lesions. Lesions of the medial dorsal raphé nuclei or injections of clonidine into the intact medial dorsal raphé nuclei did not affect the pressor response to fatiguing isometric contractions. Injections of clonidine into the intact ventrolateral medulla eliminated the pressor response to isometric contractions. Bilateral lesions of the ventrolateral medulla near the rostral lateral border of the inferior olivary tract nuclei (P12.0, LR 2.0, HD -10 mm) also attenuated the muscle pressor response, while subsequent injections of clonidine into the cerebral aqueduct depressed the changes in blood pressure further.
Ergoreceptor information may be processed through the periaqueductal grey matter through the ventrolateral medulla to control arterial blood pressure during isometric exercise to fatigue.
旨在确定中脑导水管周围灰质、中缝背核内侧或延髓腹外侧区域在等长运动期间是否参与血压和心率的整合。
用α-氯醛糖（75mg·kg-1）麻醉猫，将导管插入右颈静脉和颈动脉。使用微处理器控制的刺激器和围绕胫神经的袖状电极产生等长收缩。在中脑导水管周围灰质背侧（P1.0，LR2.0，HD + 1.5mm）或延髓腹外侧的两个部位（P12.0，RL 2.0，HD -10mm；或P12.0，RL 2.0，HD -8.5mm）制作双侧损伤。也在中缝背核内侧（P1.0，RL 0.0，HD +1.5mm）制作损伤。向脑导水管内注射可乐定，以确定在制作损伤后肌肉收缩期间它是否会发挥降压作用。一组动物仅制作一个损伤部位。向完整的延髓腹外侧（P11.5，RL 4.0，HD -8.5mm）双侧注射可乐定（250ng于0.5微升中）以进一步探索其作用。在制作损伤或注射可乐定之前和之后进行疲劳收缩，并测量动脉血压和心率的变化。每次实验后通过对脑组织的组织学检查来验证损伤部位或微量注射部位，以及损伤范围或可乐定的扩散情况。
使用20只成年猫，雌雄不限，体重2.4（标准差0.4）kg。
在对照条件下的疲劳等长收缩使平均动脉压升高45 - 50mmHg，心率升高20 - 25次·min-1。中脑导水管周围灰质背侧的双侧损伤未改变静息平均动脉压，但减弱了收缩期间的升压反应。在制作损伤后，向脑导水管内注射可乐定没有进一步的降压作用。中缝背核内侧的损伤或向完整的中缝背核内侧注射可乐定不影响对疲劳等长收缩的升压反应。向完整的延髓腹外侧注射可乐定消除了对等长收缩的升压反应。在下橄榄核束核的嘴侧外侧边界附近的延髓腹外侧双侧损伤（P12.0，LR 2.0，HD -10mm）也减弱了肌肉升压反应，而随后向脑导水管内注射可乐定进一步降低了血压变化。
在等长运动至疲劳期间，力感受器信息可能通过中脑导水管周围灰质经延髓腹外侧进行处理，以控制动脉血压。
