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本文采用原位杂交、免疫组织化学方法检测了接受足底电击结合噪声应激刺激5天的大鼠延髓、尤其是延髓头端腹外侧区(rostral ventrolateral medulla,rVLM)编码肾上腺髓质素(adrenomedullin,ADM)的肾上腺髓质素前肽原(preproadrenomedullin,ppADM)mRNA表达和ADM免疫活性(adrenomedullin immunoreactivity,ADM-IR)变化,并通过电刺激中脑导水管背侧周围灰质(dorsal periaquaductal gray of midbrain,dPAG)诱发防御性心血管反应,以及于rVLM微量注射大鼠ADM(rat adrenomedullin,rADM)及其特异性受体拮抗剂——人肾上腺髓质素(22-52)[human adrenomedullin22-52,hADM(22-52)]相结合的手段研究rVLM中ADM在应激防御性心血管反应中的可能调节作用。结果显示,在闩前1.0～3.0mm之间的延髓组织中ppADM mRNA杂交信号和ADM-IR阳性细胞在rVLM、面神经核分布最多,中缝核、巨细胞背核、舌下神经核和下橄榄核等处尚有中等量阳性细胞,而孤束核较少;应激第5天,应激组rVLM区ppADMmRNA表达和ADM免疫阳性细胞均较对照组明显增加(P<0.01);右侧dPAG电刺激(0.5ms,100Hz)后,正常大鼠动脉压(artery pressure,AP)立即由电刺激前的(116.4±8.9)mmHg升高到(140.0±9.8)mmHg,心率(heart rate,HR)也从电刺激前的(378.0±7.5)beats/min明显加快到(413.0±8.2)beats/min。停止电刺激后AP和HR快速恢复到正常水平;右侧rVLM微量注射1pmol hADM(22-52)后10、20、30min,再给予dPAG电刺激,则由电刺激引起的ΔAP、ΔHR明显降低(P<0.05,P<0.01);rVLM微量注射0.1pmol rADM后10min内引起AP明显升高,在此基础上再给予中脑dPAG电刺激,则给药后60min内由电刺激dPAG引起的ΔAP、ΔHR虽有所增加,但统计学差异无显著性。上述结果提示,大鼠急性足底电击结合噪声刺激引发应激及血压升高伴随rVLM中ADM基因表达和免疫活性的明显增加,并且阻断rVLM中ADM特异性受体可减弱电刺激dPAG引起的应激防御心血管反应。因此,rVLM中ADM可能作为一种重要的神经递质或神经调质参与了应激防御性心血管反应。
In this study, in situ hybridization and immunohistochemistry were used to detect the medulla oblongata, which was stimulated by foot shock combined with noise stress for 5 days, especially the rrenoldural medulla (rVLM) encoding adrenomedullin , Adrenomedullin immunoreactivity (ADM-IR) mRNA expression in adriamycin medulla oblongata (ADM) and dorsal periaquaductal gray of midbrain , dPAG) induced defensive cardiovascular responses, as well as rAdM microinjection of rat adrenomedullin (rADM) and its specific receptor antagonist - human adrenomedullin (22-52) [human adrenomedullin22-52, hADM (22-52)] to investigate the possible regulatory role of ADM in stress-defensive cardiovascular responses in rVLM. The results showed that ppADM mRNA and ADM-IR positive cells in rVLM and facial nerve nucleus were most distributed in medulla oblongata between 1.0-3.0 mm before the latch. The distributions of nucleus raphe nucleus, mesenchymal nucleus, hypoglossal nucleus and inferior olivary nucleus There was also a moderate number of positive cells at the locus and a few solitary nuclei. On day 5 of stress, ppADM mRNA expression and ADM immunopositive cells in rVLM were significantly increased (P <0.01), while right dPAG After stimulation (0.5 ms, 100 Hz), the arterial pressure (AP) in normal rats increased from (116.4 ± 8.9) mmHg to (140.0 ± 9.8) mmHg immediately before electrical stimulation, heart rate From (378.0 ± 7.5) beats / min before electrical stimulation to (413.0 ± 8.2) beats / min. AP and HR returned to normal level after stopping the electrical stimulation. The ΔAP and ΔHR induced by electrical stimulation were significantly decreased after the right rVLM was injected 10 min, 20 min and 30 min after 1 pmol hADM (22-52) P <0.05, P <0.01). AP induced a significant increase of AP within 10 min after microinjection of 0.1 pmol rADM into rVLM. On the basis of the dPAG stimulation, Although there was an increase in ΔHR, the statistical difference was not significant. The above results suggest that the acute foot shock combined with noise-induced triggering of stress and high blood pressure accompanied with a significant increase of ADM gene expression and immunological activity in rVLM, and blockade of ADM-specific receptors in rVLM may attenuate the effects of electrical stimulation of dPAG Stress defenses cardiovascular response. Therefore, ADM in rVLM may participate in the stress-defensive cardiovascular response as an important neurotransmitter or neuromodulator.