【摘要】 清醒大鼠侧脑室注射(icv)甲八肽酰胺(MET)可引起明显的降压和减慢心率作用。用小剂量纳洛酮(0.4mg/kg,ip)预处理可明显拮抗MET的减慢心率作用,但仅部分拮抗其降压作用。大剂量纳洛酮(10mg/kg,ip)才能翻转MET的降压作用。纳洛肼(30μg,icv)不能拮抗MET的减慢心率作用。icv强啡肽1—8可引起降压效应,但对心率无明显影响。此外,家兔icv MET引起降压作用的同时,血浆NA水平明显降低。阿托品可明显拮抗MET的减慢心率作用,但对其降压作用无明显影响。 以上结果提示,MET的减慢心率作用可能由mu 2亚型参与,mu 1亚型则否;而降压作用则由kappa和mu亚型共同参与调节。外周交感活动与MET的降压作用有关,外周迷走神经活动参与MET的减慢心率作用。更多还原

【Abstract】 Intracerebroventricular (icv) injection of metorphamide (MET) elicitedobvious hypotension and bradycardia in conscious rats. The MET induced bra-dycardia was significantly antagonized by pretrcatment of a small dose of naloxone(NX 0.4mg/kg, ip), but the MET induced hypotension was only partially an-tagonized. In order to antagonize the MET hypotension, a large dose of NX(10mg/kg, ip)was needed. ICV 30μg of naloxonazine, a relatively selective blocker ofmu 1 receptor, did not antagonize the MET bradycardia effect. Dynorphin 1-8,also induced hypotension, but there was almost no effect on heart rate. The plasmanoradrenaline levels were markedly decreased during MET induced hypotensionin rabbits. MET induced bradycardia was significantly antagonized by pretreat-ment with atropine (1mg/kg, ip), but the MET induced hypotension was almostunaffected. The results mentioned above indicate that the bradycardia effect of METmay be mediated by mu 2 subtype of opiate receptors instead of mu 1; but kappa andmu subtypes are involved in the hypotensive effect. The bradycardia effect ofMET may be mediated by vagus activity, while the hypotensive effect of EMTmay be related to sympathetic activity.更多还原