Connections between the midbrain dorsolateral periaqueductal grey (dlPAG) and the pontine A5 region have been shown. The stimulation of both regions evokes similar cardiovascular responses: tachycardia and hypertension. Accordingly, we have studied the interactions between dlPAG and A5 region in spontaneously breathing anesthetized rats. dlPAG was electrically stimulated (20–30 μA 1-ms pulses were given for 5 s at 100 Hz). Changes in the evoked cardiorespiratoy response were analysed before and after ipsilateral microinjections of muscimol (GABAergic agonist, 50 nl, 0.25 nmol, 5 s) within the A5 region. Electrical stimulation of the dlPAG produces, in the rat, a response characterized by tachypnoea (p < 0.001), hypertension (p < 0.001) and tachycardia (p < 0.001). The increase in respiratory rate was due to a decrease in expiratory time (p < 0.01). Pharmacological inhibition of the A5 region with muscimol produced a marked reduction of the tachycardia (p < 0.001) and the tachypnoea (p < 0.01) evoked from the dlPAG. Finally, to assess functional interactions between A5 and dlPAG, extracellular activity of putative A5 neurones were recorded during dlPAG electrical stimulation. Forty A5 cells were recorded, 16 of which were affected by dlPAG stimulation (40%). 4 cells showed activation, 5 cells excitation and 7 cells decreased spontaneous activity to dlPAG stimulation (p < 0.001). These results confirm a link between the A5 region and dlPAG. The potential role of these connections in the modulation of dlPAG evoked cardiorespiratory responses and their possible clinical implications are discussed.

已显示中脑背外侧水管周围灰色（dlPAG）和桥脑A5区之间的联系。两个区域的刺激引起相似的心血管反应：心动过速和高血压。因此，我们研究了自发呼吸麻醉大鼠中dlPAG与A5区之间的相互作用。电刺激dlPAG（在100 Hz下给予20-30μA1-ms脉冲5 s）。在同侧显微注射A5区域内同侧微量注射麝香酚（GABA能激动剂，50 nl，0.25 nmol，5 s）之前和之后，分析诱发的心肺复苏反应的变化。dlPAG的电刺激在大鼠中产生以呼吸急促（p  <0.001），高血压（p  <0.001）和心动过速（p <0.001）。呼吸频率的增加是由于呼气时间的减少（p  <0.01）。与蝇蕈醇的A5区域的药理学抑制产生的心动过速的显着降低（p  <0.001）和呼吸急促（p 从dlPAG诱发<0.01）。最后，为了评估A5和dlPAG之间的功能相互作用，在dlPAG电刺激过程中记录了假定的A5神经元的细胞外活性。记录了40个A5细胞，其中16个受到dlPAG刺激的影响（40％）。4个细胞显示激活，5个细胞激发，7个细胞对dlPAG刺激的自发活性降低（p <0.001）。这些结果证实了A5区域和dlPAG之间的联系。讨论了这些连接在调节dlPAG诱发的心肺反应中的潜在作用及其可能的临床意义。