5-羟色胺1A受体激动剂8-OH-DPAT改善帕金森病运动并发症的实验研究

目的 探讨5-羟色胺1A(5-HT1A)受体激动剂8-OH-DPAT对左旋多巴诱发的运动并发症的细胞学与行为学效应.方法 通过6-羟基多巴胺立体定向注射至大鼠前脑内侧前脑束建立帕金森病(Parkinson disease,PD)动物模型.对模型成功的PD大鼠进行两套实验:第1套实验中3组PD大鼠接受每日2次左旋多巴甲酯(50 mg/kg加12.5 mg/kg苄丝肼)腹腔注射,持续22 d.在第23天左旋多巴注射前,3组PD大鼠先分别接受8-OH-DPAT、8-OH-DPAT+5-羟色胺1A(5-HT1A)受体阻断剂WAY-100635(0.1 mg/kg)及溶剂对照注射;第2套实验中2组PD大鼠每日2次分别接受左旋多巴/苄丝肼+8-OH-DPAT与左旋多巴/苄丝肼+溶剂,持续22 d.评估旋转时间、关期发生频率情况;采用蛋白印迹法检测纹状体区谷氨酸受体1(GluR1)亚细胞分布及GluR1的845位丝氨酸(GluR1Ser845)磷酸化的表达情况.结果 8-OH-DPAT逆转了左旋多巴所诱导的PD大鼠旋转时间的缩短,延长约27.8%±6.1%;并使关期发生频率减少约7.2%±1.7%.5-HT1A受体阻断剂WAY-100635与8-OH-DPAT联合应用则消除了8-OH-DPAT的效应,提示所观察到的8-OH-DPAT的效应是通过5-HT1A受体起作用的.此外,8-OH-DPAT能调节与运动并发症密切相关的GluR1的亚细胞分布,且使GluR1Ser845的磷酸化水平降低约22.1%±3.5%.结论 激动5-HT1A受体的药物可能是治疗及预防PD运动并发症有益的疗法.     

帕金森病运动并发症与谷氨酸受体亚型GluR1Ser845磷酸化关系的实验研究

目的探讨帕金森病(PD)长期左旋多巴治疗的运动并发症与纹状体神经元谷氨酸受体1的845位丝氨酸(GluR1Ser845)磷酸化的关系。方法通过6-羟基多巴立体定向注射至大鼠前脑内侧前脑束建立PD动物模型,然后左旋多巴甲酯腹腔注射治疗(25mg.kg-1.d-1,每天2次)22d,评估旋转时间、关期发生频率情况;采用免疫荧光与蛋白印迹法检测纹状体区谷氨酸受体1(GluR1)亚细胞分布及GluR1Ser845磷酸化的表达情况。结果PD大鼠长期应用左旋多巴处理后呈现旋转时间逐渐缩短、关期频率递增的趋势,与人类症状波动和开关现象具有相似特征。PD大鼠损伤侧纹状体细胞膜上GluR1和GluR1Ser845磷酸化的数量分别减少至73.0%±4.8%和42.0%±5.6%;长期左旋多巴处理后使损伤侧纹状体细胞膜上GluR1和GluR1Ser845磷酸化的数量分别增加至104.0%±5.5%和112.0%±3.4%;然而损伤侧纹状体GluR1总蛋白数量未发生明显变化。这些改变特异性发生在小清蛋白阳性的中间神经元上。结论长期左旋多巴治疗的运动并发症可能与小清蛋白阳性的神经元上GluR1的亚细胞分布及GluR1Ser845磷酸化的改变有关。     

ERK通路参与可持续释放左旋多巴微球减少帕金森病运动并发症的实验研究

目的观察聚乳酸-羟基乙酸共聚物(PLGA)包裹的可释放左旋多巴/苄丝肼的微球对帕金森病(PD)大鼠运动症状及异动症发生的影响并探讨其机制。方法利用PLGA包裹左旋多巴或苄丝肼制成微球,采用高效液相法测定微球在大鼠体外释放左旋多巴/苄丝肼的浓度。6-羟基多巴胺(6-OHDA)腹腔注射制备PD大鼠模型,将造模成功的PD大鼠分为PD组、左旋多巴处理组和微球处理组,并设假手术组,各组12只。给予左旋多巴处理组大鼠皮下注射左旋多巴(12mg/kg)和苄丝肼(15mg/kg),给予微球处理组大鼠皮下注射含同等剂量左旋多巴和苄丝肼的微球。于治疗的第1、7、14天计数大鼠经阿扑吗啡诱导的旋转圈数。2周后行大鼠异常不自主评分(AIM)并利用Western blot检测大鼠纹状体区细胞外信号调节激酶(ERK1/2)的磷酸化水平。结果体外释放试验结果显示微球内的左旋多巴/苄丝肼均匀缓慢释放,第7天时左旋多巴和苄丝肼释放量分别达到91.2%%和97.1%。治疗2周后,微球处理组大鼠和左旋多巴处理组大鼠阿扑吗啡诱导的旋转圈数均明显下降(均P<0.05),但在治疗的第1、7、14天两组比较无明显统计学差异。微球处理组大鼠于治疗后的第1、2、4、6、8、10、12、14天的AIM评分(轴性+上肢+口面)与左旋多巴处理组大鼠有统计学差异(均P<0.05)。Western blot结果显示左旋多巴处理组大鼠纹状体ERK1/2水平较PD组和假手术组明显升高(均P<0.05)。微球处理组大鼠纹状体ERK1/2磷酸化水平较左旋多巴处理组大鼠明显降低(P<0.01)。结论微球皮下注射可以改善PD大鼠的运动症状,同时可以减少PD大鼠异动症的发生,这可能与微球释放的左旋多巴持续性刺激PD大鼠从而减少ERK1/2的磷酸化水平有关。     

可控释左旋多巴和苄丝肼微球减少帕金森病大鼠异动症的发生

目的 观察聚乳酸-羟基乙酸共聚物( PLGA)包裹的可释放左旋多巴和苄丝肼的微球对帕金森病(PD)大鼠运动症状及异动症发生的影响并探讨其机制.方法 PLGA包裹左旋多巴及苄丝肼制作微球,高效液相法测定微球在体内释放出的左旋多巴和苄丝肼的浓度,6-羟基多巴胺(6-OHDA)注射制作PD大鼠模型,制模成功的PD大鼠随机分成PD组、左旋多巴组、微球组(每组12只),另设溶剂注射假手术组(n=12).左旋多巴组和微球组大鼠分别接受左旋多巴和苄丝肼(左旋多巴12 mg/kg,苄丝肼15 mg/kg)或等剂量微球皮下注射,在治疗的第1、4、7、10、14天行大鼠前肢功能测定,治疗2周后行大鼠异常不自主运动( AIM)评分,免疫组织化学及Western blot法检测纹状体区磷酸化的多巴胺和环磷腺苷调节的磷酸化蛋白-32(DARPP-32)(Thr34)和△FosB水平.结果 体内释放实验表明第7天时左旋多巴和苄丝肼释放量分别达76.2％和83.6％.微球处理组大鼠在治疗的第10天和第14天时前肢跨步数分别为5.8±1.6和5.2±1.5,比左旋多巴组(2.4±1.1、1.2±0.5)明显增加(t =4.12,5.43,均P＜0.01).微球处理组大鼠第14天AIM评分[(16.0±2.1)分]较左旋多巴处理组[(26.0±3.2)分]显著下降,差异有统计学意义(t =6.59,P＜0.01).免疫组织化学显示微球处理组大鼠纹状体磷酸化DARPP-32水平[(3.7±1.3)×104]较左旋多巴处理组[(7.9±2.2)×104]明显降低(t=2.95,P＜0.05).Western blot结果显示微球处理组大鼠磷酸化DARPP-32和△FosB水平分别为119.4％±11.3％和149.3％±12.3％,较左旋多巴组(184.8％±13.7％和300.4％±14.2％)显著下降(t =4.12、2.91,均P＜0.05).结论 微球皮下注射可以改善PD大鼠的运动症状,同时可以减少PD大鼠异动症的发生,这与微球释放的左旋多巴持续性刺激PD大鼠从而减少磷酸化DARPP-32和△FosB的水平有关.     

包裹左旋多巴/苄丝肼PLGA微球通过Tau蛋白/△FosB信号通路治疗异动症大鼠的实验研究

目的 探讨可缓释包裹左旋多巴/苄丝肼微球对异动症大鼠的治疗作用及其机制.方法 通过注射6-羟基多巴胺(6-OHDA)制作帕金森病(Parkinson disease,PD)大鼠模型,制模成功的PD大鼠模型接受左旋多巴(25mg/kg)/苄丝肼(12.5mg/kg)腹腔注射21 d制作异动症大鼠模型.将异动症大鼠分成普通剂型组(n=13)和微球组(n=13)两组.普通剂型组给予普通剂型左旋多巴/苄丝肼皮下注射(按体质量左旋多巴12 mg/kg、苄丝肼15mg/kg),微球组给予等剂量包裹左旋多巴/苄丝肼微球皮下注射.分别于治疗第1、5、10、15和第20天,在大鼠腹腔注射阿扑吗啡后计数其旋转圈数,并于治疗3周后对大鼠进行异常不自主运动(AIM)评分(包括上肢、口面部和轴性3部分).另设PD组和假手术组大鼠各13只.以Western Blot检测大鼠纹状体区△FosB、Tau蛋白和磷酸化Tau蛋白水平,免疫组织化学法测定大鼠纹状体区磷酸化Tau蛋白阳性细胞水平.结果 普通剂型组大鼠在治疗后的第1、5、10、15和20天阿扑吗啡诱导的旋转圈数分别为221±34.4、180±25.4、123±17.3、91±13.1、84±10.7,微球组大鼠的旋转圈数分别为223±35.1、172±26.8、131±18.7、97±14.9、82±10.5,两组各时点分别比较差异均无统计学意义(P＞0.05).微球组大鼠轴性AIM、上肢AIM、口面AIM评分分别为6.5±0.9、4.1±0.5、5.8±0.7,均低于普通剂型组大鼠(分别为10.3±1.9、6.3±0.9、8.2±1.2)(均P＜0.05).Western blot结果显示,普通剂型组大鼠纹状体△FosB水平[(620.7±48.3)％]高于PD组[(290.2±31.5％)](t=2.11,P＜0.05),但低于微球组[(320.5±32.8)％](t=4.56,P＜0.01).普通剂型组纹状体区磷酸化Tau蛋白水平[(340.4±27.1)％]高于PD组[(130.4±21.5)％](t=2.67,P＜0.05),微球组[(134.6±14.1)％]低于普通剂型组(t=4.13,P＜0.01).免疫组化结果示,普通剂型组大鼠纹状体区磷酸化Tau蛋白阳性细胞指数为(14.6±2.3)×104,高于PD组[(6.9±1.1)×104](t=3.98,P＜0.01),微球组[(7.2±1.1)×104]明显低于普通剂型组(t=3.76,P＜0.01).结论 微球治疗减轻了异动症大鼠的症状,其原因可能是由于可缓释包裹左旋多巴/苄丝肼微球通过影响Tau蛋白/△FosB信号通路的活性,进而改善了异动症大鼠的症状.     

CB1受体激动剂WIN55212-2改善帕金森病运动并发症的实验研究

目的探讨CB1受体激动剂WIN55212-2对左旋多巴诱发的运动并发症的行为学及细胞学作用。方法通过6-OHDA立体定向注射至大鼠右侧前脑内侧束建立PD动物模型,成功的PD大鼠模型分别接受左旋多巴/苄丝肼(50mg/kg加12.5mg/kg苄丝肼,每天2次)+溶剂、左旋多巴/苄丝肼+WIN55212-2(1mg/kg)腹腔注射,共持续21d。评估用药后大鼠的旋转反应时间、剂峰旋转圈数变化和关期发生率;采用Western blot方法检测纹状体信号转导蛋白DARPP-32(Thr75)和ERK1/2(Thr202/Tyr204)的磷酸化表达。结果长期联合应用WIN55212-2和左旋多巴,缓解了左旋多巴单独用药所致的PD大鼠旋转反应时间缩短、剂峰旋转圈数增加的趋势,并明显降低关期发生频率。WIN55212-2与左旋多巴合用显著降低了纹状体内DARPP-32(Thr75)的磷酸化;但未使ERK1/2磷酸化表达降低至对照组水平。结论激动CB1受体可能有益于预防帕金森病运动并发症。     

腺苷A2A受体拮抗剂改善帕金森病运动并发症

目的 探讨腺苷A2A受体拮抗剂8-(3-Chlorostyryl)caffeine(CSC)对左旋多巴诱发的运动并发症的行为学与细胞学影响.方法 通过6-羟基多巴(6-OHDA)立体定向注射至大鼠前脑内侧束建立帕金森病(PD)动物模型.模型成功大鼠接受每日2次左旋多巴甲酯(50 mg/kg加12.5mg/kg苄丝肼)腹腔注射,持续22 d.在第23天,运动并发症模型组大鼠(n=8)继续接受如上用药,用药组(n=8)在左旋多巴注射前注射腺苷A2A受体拮抗剂CSC,均用药至第29天.同时设假手术组(n=8)和PD对照组(n=8).评估旋转时间,并采用免疫组织化学法和蛋白印迹法观察和检测纹状体区腺苷A2A受体的表达情况.结果 左旋多巴长期用药诱发PD大鼠模型旋转反应时间缩短,同时模型组损伤侧纹状体区腺苷A2A受体的表达升高[阳性细胞指数(IOD),(11.55±2.75)×104>],较假手术组[IOD,(6.02±1.29)×10±]和PD组[IOD,(5.60±1.83)×10±]有统计学意义(F=33.31,P<0.05).CSC用药逆转了左旋多巴诱导的PD大鼠旋转时间的缩短,损伤侧纹状体区腺苷A2A受体的表达[IOD,(5.80±1.56)×104>]也下调至对照组和PD组水平.结论 腺苷A2A受体参与了左旋多巴诱发的运动并发症的发生,腺苷A2A受体拮抗剂可能是治疗PD运动并发症有前景的药物.     

抗帕Ⅰ号方剂对帕金森病大鼠纹状体多巴胺受体的影响

目的探讨抗帕Ⅰ号方剂对帕金森病(PD)大鼠纹状体多巴胺D1(DR1)、D2受体(DR2)表达的影响.方法 6-羟基多巴胺损毁制备偏侧PD大鼠模型,PD大鼠分为4组,分别进行抗帕Ⅰ号方剂、左旋多巴甲酯/苄丝肼、左旋多巴甲酯/苄丝肼/抗帕Ⅰ号方剂和生理盐水灌胃治疗4周,观察大鼠行为学变化;RT-PCR检测纹状体DR1、DR2受体的表达.结果抗帕Ⅰ号方剂联合左旋多巴治疗使PD大鼠产生稳定的对侧旋转行为;左旋多巴治疗后使PD大鼠在盐酸去水吗啡诱发后产生逐步增加的对侧旋转行为;联合抗帕Ⅰ号方剂及左旋多巴治疗可使盐酸去水吗啡诱发的对侧旋转次数减少.联合左旋多巴及抗帕Ⅰ号方剂治疗后损毁侧纹状体DR1 mRNA表达较对照组、抗帕Ⅰ号方剂组增强(P<0.05),而DR2 mRNA表达较对照组、抗帕Ⅰ号方剂组减弱(P<0.05).结论联合抗帕Ⅰ号方剂及左旋多巴治疗可改善PD大鼠行为学,但单独应用抗帕Ⅰ号方剂对多巴胺受体表达无明显影响,且抗帕Ⅰ号方剂无明显受体激动剂的作用.     

细胞外信号调节激酶通路在帕金森病运动并发症中的作用

目的 探讨细胞外信号调节激酶(ERK)通路在左旋多巴诱发的运动并发症中的作用.方法 通过6-羟多巴胺立体定向注射至大鼠前脑内侧前脑束建立帕金森病(PD)动物模型.对建模成功的PD大鼠每日2次左旋多巴(50 mg/kg 加12.5 mg/kg苄丝肼)腹腔注射,持续22 d.在第23天注射左旋多巴前,给予PD大鼠ERK特异性的抑制剂PD98059处理.评估旋转反应时间及剂峰旋转圈数,采用蛋白免疫印迹法检测纹状体区ERK1/2 磷酸化表达情况.结果 长期使用左旋多巴处理使PD大鼠损伤侧纹状体ERK1/2 磷酸化水平显著增强(155.6%±6.5%), 而PD98059 可明显降低ERK1/2磷酸化水平(85.4%±5.6%).同时,PD98059逆转了左旋多巴所诱导的PD大鼠旋转时间的缩短,减少了剂峰旋转次数.此外,蛋白激酶C(PKC)抑制剂能部分减轻ERK1/2磷酸化水平(101.2%±6.2%,与左旋多巴+溶剂组相比较t=3.2,P<0.05).结论 PD运动并发症的发生可能与纹状体ERK通路的激活有关,并且ERK通路的激活部分是PKC所依赖的;抑制ERK通路活性的药物可能是治疗PD运动并发症的一种新的治疗方式.     

5-羟色胺1A受体激动剂8-OH-DPAT对癫痫合并抑郁神经发生的研究

目的探讨5-羟色胺1A(5-HT1A)受体与匹罗卡品诱导的癫痫大鼠合并抑郁海马齿状回神经发生的关系。方法从匹罗卡品诱导的慢性自发性颞叶癫痫大鼠中筛选出合并抑郁的大鼠3 2只,随机分成模型组、卡马西平(CBZ)组、CBZ+8-OH-DPAT低剂量(0.1 mg/kg)组、CBZ+8-OH-DPAT高剂量(1.0 mg/kg)组,每组8只。对照组8只,注射生理盐水(1 0 m l/kg)。药物干预后,制备大鼠脑片,利用免疫组织化学方法检测大鼠的神经发生。结果模型组海马齿状回神经发生较对照组明显增多,差异有统计学意义(P<0.0 5)。CBZ组、CBZ+8-OH-DPAT低剂量组、CBZ+8-OH-DPAT高剂量组较模型组神经发生明显增多,差异有统计学意义(P<0.0 5)。CBZ+8-OH-DPAT高剂量组较CBZ组、CBZ+8-OH-DPAT低剂量组神经发生明显增多,差异有统计学意义(P<0.0 5)。但CBZ组与CBZ+8-OH-DPAT低剂量组比较神经发生的差异没有统计学意义(P>0.0 5)。结论高剂量的5-HT1A受体激动剂8-OH-DPAT在实验的过程中能够增加癫痫合并抑郁大鼠的神经发生。     

CYP1A1 and GSTM1/T1 Genetic Variation in Predicting Risk for Cerebral Infarction

Cytochrome P450 1A1 (CYP1A1) is involved in the production of arachidonic acid-derived vasoactive substance. We hypothesized that CYP1A1 polymorphism might be related to pathological conditions associated with cerebral infarction (CI). We investigated the effect of genetic polymorphism in the 3′-flanking region (T6235C) of CYP1A1 gene in 353 patients with CI and 376 controls. The distributions of T6235C CYP1A1 genotypes in patients with (TT: 36.0%; TC/CT: 64.0%; n = 353) and without CI (TT: 44.7%; TC/CT: 55.3%; n = 376) indicate that the C allele is associated with CI (P = 0.017, odds ratio (O.R.) = 1.44; 95% confidence interval (C. I.) = 1.07–1.94). Furthermore, we examined whether the glutathione S-transferase (GST) gene, which is one of detoxification enzyme, influence the risk of CI. GST M1 null genotype increased the relative risk for the CI in the subjects with the CYP1A1 C allele (P = 0.015, O.R. = 1.47; C. I. = 1.08–2.00). We conclude that T6235C CYP1A1 polymorphism is a risk factor for the development of CI and suggest that GST polymorphism contribute to the odds of CI.     

Adult GM1 gangliosidosis--biochemical studies--1]

To address the pathogenesis of GM1 gangliosidosis, especially adult form, intracellular signal transduction pathway of EGF in skin fibroblasts from patients with this disorder was examined. For this purpose, skin fibroblasts from 2 different patients with adult form of the disorder and from 4 different normal controls were used. The results showed that 1) EGF-receptor autophosphorylation was diminished in skin fibroblasts from patients with altered time course of phosphorylation-dephosphorylation reaction. 2) The amount of EGF-receptor protein was decreased in cells from patients compared with that of controls. 3) 125I-EGF binding + internalization studies revealed decreased rate of EGF binding and internalization in patient cells. 4) Ribosomal S6 protein phosphorylation was strongly enhanced in naive cells from patients, but the reactivity to EGF was diminished compared with control cells. These data strongly suggest that patient fibroblasts have abnormalities in the intracellular signal transduction pathway of EGF. This paper is considered to be the first report demonstrating abnormalities in EGF-signal transducing system in human disorders.     

Polycystin-1 can interact with homer 1/Vesl-1 in postnatal hippocampal neurons

Polycystin-1 (PC-1) has been identified as critical to development of the nervous system, but the significance of PC-1 expression in neurons remains undefined, and little is known of its roles outside the kidney, where mutation results in autosomal dominant polycystic kidney disease (ADPKD). In kidney, PC-1 interacts with cadherins, catenins, and its cognate calcium channel polycystin-2 (PC-2), which in turn interacts with a number of actin-regulatory proteins. Because some of the proteins that interact with PC-1 in kidney also participate in synaptic remodeling and plasticity in the hippocampus, we decided to test PC-1's potential to interact with a recently discovered type of plasticity-associated protein (homer 1a/Vesl-1S) in postnatal mouse hippocampus. Homer 1a/Vesl-1S is an activity-induced protein believed to participate in synaptic remodeling/plasticity responses to temporal lobe seizure and learning. Here we report the following. 1) PC-1 contains a homer-binding motif (PPxxF), which lies within its purported cytoplasmic domain. 2) Immunoreactivity for PC-1 (PC-1-ir) is highly colocalized with homer 1a immunoreactivity (H1a-ir) in primary cultured hippocampal neurons. 3) PC-1-ir and H1a-ir are present and appear to be colocalized in mouse hippocampus but not cortex on postnatal day 2 (P2), when higher frequencies of spontaneous activity are normal for hippocampus compared with cortex. 4) An endogenous PC-1-ir band with the correct size for the reported C-terminal G-protein-sensitive domain cleavage product of PC-1 (approximately 150 kDa) coimmunoprecipitates with endogenous homer 1/Vesl-1 proteins from mouse brain, suggesting that PC-1 can interact with homer 1/Vesl-1 proteins in postnatal hippocampal neurons.     

DRB1*1502-DQB1*0601-DQA1*0103 and DRB1*04-DQB1*0302 in Jewish hypersomnolent patients

OBJECTIVES: Narcolepsy is a sleep disorder with a genetic association with the haplotype DRB1*1501, DQA1*0102, DQB1*0602. This haplotype has been described in different ethnic groups suffering from narcolepsy (Japanese, Caucasian, African Americans, Jews). In a recent study we have found the haplotype DRB1*1502, DQB1*0601, DQA1*0103 in three patients with hypersomnolence. The similarity of this haplotype to the narcoleptic haplotype DRB1*1501, DQB1*0602 and DQA1*0102 has raised the question of whether this haplotype is a marker for sleepiness, or rather indicates a variant of non-cataplectic narcolepsy. This study was conducted to further investigate this question. METHODS: HLA-DNA analysis was carried out in 20 healthy Jewish patients (age 23.9+/-6.3 years; 13 Ashkenazi, seven non-Ashkenazi) who had objective measures of hypersomnolence. All underwent whole-night polysomnography, multiple sleep latency test and tissue typing. RESULTS: HLA-DNA analysis revealed HLA-DR2 in eight patients of whom five (25%) carried the haplotype DRB1*1502, DQB1*0601, DQA1*0103 (vs. 1.4% in the Israeli population, P<0.0001). Six patients were diagnosed as non-cataplectic narcoleptics. Five of them carried the haplotype DRB1*1502, DQB1*0601, DQA1*0103. Forty percent of the patients carried the haplotype DRB1*04, DQB1*0302, which was not statistically different from its prevalence in the healthy Israeli population (25%). CONCLUSIONS: This is the first report describing the haplotype DRB1*1502, DQB1*0601, DQA1*0103 in narcoleptic patients (non-cataplectic). This haplotype is close but different from the already known narcoleptic haplotype DRB1*1501, DQA1*0102, DQB1*0602. We assume that this haplotype represents a variant of non-cataplectic narcolepsy rather than association with hypersomnolence. However, in order to conclude whether this haplotype is a marker for the lack of cataplexy, or represents a variant of non-cataplectic narcolepsy, a larger group of patients should be investigated.     

Bace 1

Adrenomedullin (AM) has two specific receptors formed by the calcitonin-receptor-like receptor (CL) and receptor activity-modifying protein (RAMP) 2 or 3. These are known as AM₁ and AM₂ receptors, respectively. In addition, AM has appreciable affinity for the CGRP₁ receptor, composed of CL and RAMP1. The AM₁ receptor has a high degree of selectivity for AM over CGRP and other peptides, and AM_22–52 is an effective antagonist at this receptor. By contrast, the AM₂ receptor shows less specificity for AM, having appreciable affinity for βCGRP. Here, CGRP_8–37 is either equipotent or more effective as an antagonist than AM_22–52, depending on the species from which the receptor components are derived. Thus, under the appropriate circumstances it seems that βCGRP might be able to activate both CGRP₁ and AM₂ receptors and AM could activate both AM₁ and AM₂ receptors as well as CGRP₁ receptors. Current peptide antagonists are not sufficiently selective to discriminate between these three receptors. The CGRP-selectivity of RAMP1 and RAMP3 may be conferred by a putative disulfide bond from the N-terminus to the middle of the extracellular domain of these molecules. This is not present in RAMP2.