Schenberg L C, Lovick T A
Department of Physiology, Medical School, University of Birmingham, UK.
Brain Res. 1994 Jul 18;651(1-2):236-40. doi: 10.1016/0006-8993(94)90702-1.
In rats anaesthetised with alphaxalone/alphadolone, electrical stimulation in the dorsolateral part of the periaqueductal grey matter (PAG; 10 s trains of 1 ms pulses at 80 Hz, 40-80 microA) evoked a pressor response accompanied by tachycardia. Both components of the response were attenuated following microinjection of 200 nl 0.1 M D,L-homocysteic acid into the caudal pole of the nucleus raphe magnus (NRM; n = 12) and into the nucleus raphe obscurus (NRO; n = 22) to selectively activate neuronal perikarya. Microinjection of 200 nl 165 mM NaCl into the same region (n = 15) had no effect. The attenuation of the midbrain-evoked cardiovascular responses lasted for 10-20 min and was independent of changes in resting blood pressure and heart rate. The maximum reduction in the pressor component of the midbrain-evoked responses was similar following stimulation in NRM (-35.4%) and NRO (-36.7%). However, the reduction in the midbrain-evoked tachycardia was greater following stimulation in NRM (-62.8%) compared to NRO (-27.2%). These results indicate that neurones in NRM and NRO may be involved in modulating the level of excitability of the midbrain defence area in the PAG and/or its efferent pathway.
在用α-羟孕酮/α-多沙孕酮麻醉的大鼠中，刺激导水管周围灰质（PAG）背外侧部分（以80Hz的频率施加1ms脉冲，持续10s，强度为40-80微安）会诱发升压反应并伴有心动过速。在向中缝大核（NRM；n = 12）尾极和中缝隐核（NRO；n = 22）微量注射200nl 0.1M D，L-高胱氨酸以选择性激活神经元胞体后，反应的两个成分均减弱。向同一区域微量注射200nl 165mM NaCl（n = 15）则无影响。中脑诱发的心血管反应减弱持续10-20分钟，且与静息血压和心率的变化无关。在NRM刺激后（-35.4%）和NRO刺激后（-36.7%），中脑诱发反应的升压成分的最大降低相似。然而，与NRO（-27.2%）相比，在NRM刺激后中脑诱发的心动过速的降低幅度更大（-62.8%）。这些结果表明，NRM和NRO中的神经元可能参与调节PAG中脑防御区及其传出通路的兴奋性水平。
