AVP V1受体阻断剂对昼光和暗光中正常大鼠体温的影响

目的: 研究内源性精氨酸加压素(AVP)是否参与正常的体温调节过程。方法: 用无线体温遥测仪测量大鼠的体温变化,观察腹腔注射AVPV₁受体阻断剂对昼光和暗光中(明∶暗=12∶12)大鼠体温的影响。结果: 腹腔注射AVPV₁受体阻断剂可明显提高大鼠的正常体温,在昼光中(6:00AM-6:00PM)体温升高持续的时间长达6h,雄性大鼠的体温明显高于雌性的体温。在暗光中(6:00PM-6:00AM),AVPV₁受体阻断剂只使进入暗光初期的大鼠体温升高,持续的时间为2h,雄性和雌性之间无明显差别。结论: AVPV₁受体阻断剂可使正常大鼠体温升高,实验结果提示内源性AVP对正常体温有紧张性调节作用。     

内源性精氨酸加压素在索曼引起的大鼠体温降低中的作用

目的:探讨内源性精氨酸加压素是否参与索曼引起的降温过程。方法:用数字体温计测量大鼠的体温,每次间隔60 min,观察了腹腔注射AVP V₁受体阻断剂(30 μg/kg)对皮下注射索曼(60 μg/kg)引起大鼠降温效应的影响,以及给索曼后2 h血浆中AVP含量的变化。结果:给索曼后可引起明显的体温降低,在给药后7 h体温恢复到基线水平。AVP V₁受体阻断剂能明显阻断索曼的降温效应。在给索曼后2 h血浆中AVP浓度明显提高。结论:实验结果证明内源性AVP参与索曼引起的降温过程。     

精氨酸加压素翻转脂多糖引起大鼠发热及其对痛觉敏感性的影响

目的:研究外周给精氨酸加压素(AVP)对脂多糖(LPS)引起的大鼠发热和痛觉过敏的影响,以及与血清中IL-1β和PGE_2水平变化的关系。方法:实验用成年雄性SD大鼠,在23℃环境温度下,明暗时间各12 h。用无线遥测系统连续测量大鼠体核温度(Tc)、棕色脂肪温度(T_(BAT))和活动。10:00或11:30分别给大鼠腹腔注射LPS(50μg/kg)、AVP(10μg/kg)或V1a受体阻断剂(30μg/kg)。用ELISA法测定血清IL-1β和PGE_2的含量。用足底痛觉测试仪(Hargreaves test)测试大鼠热痛缩爪潜伏期的变化。结果:(1)腹腔注射LPS引起大鼠双相发热过程伴有痛觉过敏现象。(2)AVP能够翻转LPS引起的Tc和T_(BAT)升高反应,降低发热引起的痛觉敏感性。(3)外周给V1a受体阻断剂能提高LPS引起的发热反应,但不影响发热引起的痛觉敏感性变化。(4)AVP能抑制LPS引起的发热大鼠血液中IL-1β和PGE_2水平升高。结论:(1)外周给予AVP可通过抑制棕色脂肪产热以及降低血液中IL-1β和PGE_2的浓度而翻转LPS发热反应并降低发热伴随的痛觉敏感性升高现象。(2)内源性AVP也有限制LPS发热的作用,但可能不影响发热引起的痛觉阈值降低现象。     

不同环境温度对精氨酸加压素引起的大鼠低温的影响及其与尾部散热变化的关系

 目的：探讨不同环境温度对精氨酸加压素（AVP）引起的大鼠低温及其与尾部散热变化的关系,以确定是否外周给予AVP能提高大鼠尾部散热反应。方法：实验用成年雄性SD大鼠,在3种不同环境温度（12 ℃、22 ℃和32 ℃）下,用无线遥测技术连续记录体核温度和尾部皮肤温度。上午10:00给大鼠腹腔注射AVP(10 μg/kg)或V1a受体阻断剂(30 μg/kg)。同时观察AVP或V1a受体阻断剂对大鼠背斜方肌微血管直径和理毛行为的影响。结果：(1)在3种不同环境温度中,AVP引起大鼠低温均伴有尾部皮肤温度降低反应。(2) V1a受体阻断剂能够阻断AVP引起低温和尾部皮肤温度降低效应。(3)AVP能明显引起背斜方肌微血管收缩反应。(4)AVP能提高大鼠的理毛行为(唾液理毛),而且这种作用也能被外周给予V1a受体阻断剂所阻断。(5)内源性AVP不参与正常大鼠尾部散热过程。结论：外周给予AVP引起大鼠低温,不是由于其降低了体温调定点,可能是由于其抑制了体温调节性产热和提高唾液理毛活动以增加体表蒸发散热所致。     

低钠灌流时豚鼠心室肌细胞内钾离子活度和膜电位的变化及pH的影响

目的:进一步观察低钠液(低[Na]_o)灌流引起心肌细胞内钾离子活度(aⁱK)及膜电位(V_m)的变化,探讨其变化的机制及相互关系,以及pH的影响。方法:在豚鼠心室肌,应用普通及钾离子选择性微电极技术测定不同浓度低[Na]_o灌流时的V_m和aⁱK。结果:不同浓度的低[Na]_o引起了不同程度的aⁱK下降及V_m增加,并分别在不同的变化水平达到稳定。低[Na]_o可增加心肌细胞的静息电位(RP)和收缩活动,缩短动作电位时程(APD),但不影响动作电位幅度(APA)。在低[Na]_o的pH由7.4降至7.0时,aⁱK的下降减小,而对V_m的增加无影响。结论:aⁱK的下降和V_m的增加与灌流液Na⁺浓度呈良好的线性关系,而每一种低[Na]_o都可以使aⁱK和V_m在变化的水平上达到新的平衡。     

中枢CRH在大鼠应激性体温升高和LPS性发热机制中的作用

目的:进一步观察中枢促肾上腺皮质激素释放激素(CRH)在大鼠应激性体温升高和脂多糖(LPS)性发热中枢机制中的作用。方法:第三脑室微量注射CRH受体拮抗剂α-helicalCRH(9-41)和LPS,测定大鼠结肠温度及脑腹中隔区精氨酸加压素(AVP)含量。结果:生理盐水对照组大鼠体温明显升高,最大升幅为(0.88±0.31)℃。第三脑室注射CRH受体拮抗剂α-helicalCRH(9-41)10min后再注射生理盐水组,90min内大鼠结肠温度未见明显波动,90min后体温开始上升,1.5h体温反应指数(TRI_1.5)明显低于生理盐水对照组,而脑腹中隔区AVP含量和TRI_3.5与对照组比较均没有明显差别。第三脑室注射300ng的LPS引起大鼠结肠温度双相性升高,其TRI_3.5明显高于生理盐水对照组。事先向第三脑室注射α-helicalCRH(9-41)(5μg)再注射LPS组,TRI_3.5明显高于LPS组,而脑腹中隔区AVP含量明显低于LPS组。结论:CRH介导应激诱导的早期体温升高。CRH可能通过诱导脑腹中隔区AVP的生成限制大鼠LPS性发热。在大鼠LPS性发热中,CRH可能是一种双相作用分子,一方面本身介导发热体温升高,另一方面又诱生发热体温负调节介质而限制发热体温的升高。     

大鼠尾加压素Ⅱ收缩大鼠离体肺主动脉环与MAPK相关

目的:研究大鼠尾加压素II(U-II)对大鼠离体肺主动脉环的收缩效应及与细胞信号转导通路丝裂素活化蛋白激酶(MAPK)的关系。方法:从雄性Sprague-Dauley大鼠中分离出肺主动脉, 切成3-4 mm的血管环, 制备大鼠U-II(0.03-30 nmol/L)的浓度-效应收缩曲线, 另外, 用大鼠U-II(30 nmol/L)预收缩血管达平台期后, 加入MAPK阻断剂PD 98059, 制备PD 98059(0.1 μmol/L-10 μmol/L) 浓度-效应舒张曲线, 最后分别计算EC₅₀和E_max。结果:大鼠U-II是大鼠离体肺主动脉环的有效血管收缩剂[EC₅₀=7.95±0.40, E_max=(14.28±6.34)%, 以60 mmol KCl的收缩幅度为100%];PD 98059呈浓度依赖性舒张大鼠U-II预收缩的动脉[EC₅₀=5.91±0.45, E_max=(81.39±13.65)%]。结论：大鼠尾加压素II是大鼠肺主动脉有效的血管收缩剂, 细胞信号转导通路MAPK的激活参与其收缩效应。     

血管紧张素Ⅱ受体在大鼠肝星状细胞上的表达

目的: 了解血管紧张素Ⅱ的I_a亚型受体(AT_1a)在大鼠肝星状细胞中的表达情况。方法: 大鼠肝脏经链霉蛋白酶和Ⅳ型胶原酶循环灌注后, 以11% Nycodenz密度梯度离心, 分离获得肝星状细胞。提取肝星状细胞的总核糖核苷酸(RNA), 以逆转录-聚合酶链式反应(RT-PCR)技术和PCR产物测序方法检测AT_1a表达。结果: 采用RT-PCR技术检测到大鼠肝星状细胞有AT_1a mRNA表达, 且PCR产物的测序结果与GenBank上AT_1a cDNA序列有94%的一致性。结论: AT_1a mRNA在大鼠肝星状细胞上表达, 从而又为探索肝纤维化的发生机制提供了有力的依据。     

Zacopride增强心肌内向整流钾电流(IK1)效应的受体和信号转导通路

目的: 探讨5-HT₄受体激动剂兼5-HT₃受体阻断剂zacopride增强心肌内向整流钾电流(I_K1)效应的受体和细胞信号转导机制。方法: 应用全细胞膜片钳技术记录大鼠心室肌细胞膜I_K1电流,分别观察10 μmol/L 5-HT₄受体阻断剂 RS23597-190、10 μmol/L 5-HT₃受体激动剂间氯苯双胍(m-CPBG)、5 μmol/L PKA 抑制剂 KT5720、5 μmol/L PKC 抑制剂GF109203x 和 5 μmol/L PKG抑制剂 KT5823对zacopride 增强I_K1的影响。结果: 10 μmol/L 5-HT₄受体阻断剂RS23597-190本身可抑制I_K1电流,在预先应用RS23597-190的基础上,1 μmol/L zacopride仍可明显激动I_K1通道,使其内向电流(-100 mV)增强32.5% (P< 0.05)。10 μmol/L 5-HT₃受体激动剂m-CPBG对I_K1电流无明显影响,也不能逆转1 μmol/L zacopride对I_K1的增强效应(P> 0.05)。此外,5 μmol/L PKA 阻断剂 KT5720能显著抑制1 μmol/L zacopride对I_K1的增强效应(P< 0.05),而PKC 阻断剂GF109203x和PKG阻断剂KT5823则对1 μmol/L zacopride的效应无明显影响(P> 0.05)。结论: Zacopride对 I_K1的增强作用可能经由PKA介导的信号转导通路,而不依赖于5-HT₃和5-HT₄受体。     

AVP V1阻断剂对有机磷杀虫剂毒死蜱降温效应的阻断作用

目的给动物口饲有机磷农药杀虫剂毒死蜱(CHP)先出现快速的降温相,然后出现发热相.众所周知精氨酸加压素(AVP)是体内一种重要内源性抗热物质.为此本实验观察了精氨酸加压素V1受体阻断剂(AVPV1阻断剂)对CHP引起的降温效应和发热效应的影响,旨在探讨CHP对体温影响是否与AVP有关.方法实验用SD大鼠分为4组,每组7只,即对照组、CHP组、AVPV1阻断剂组和CHP-AVPV1阻断剂组.用体温遥测系统测量大鼠的体温和活动的变化.给药途径和药物剂量分别给大鼠口饲CHP30mg/kg(30g/L玉米油)或玉米油1mL/kg后,立即腹腔注射AVPV1阻断剂20μg/kg(30mg/L生理盐水)或生理盐水1mL/kg.结果给大鼠口饲CHP后可以引起快速的降温效应,给药后5h后体温由给药前的(37.75±0.11)℃降低到(36.34±0.22)℃,平均降低达1.44℃;而给CHP后立即给AVPV1阻断剂时,大鼠体温由给药前的(37.55±0.17)℃降低到(37.19±0.14)℃,平均只降低了0.46℃.对照组动物在给药后,则出现短暂的应激性体温升高和活动增加现象.AVPV1阻断剂对CHP的发热相无明显影响.在实验中发现AVPV1阻断剂也可提高正常大鼠的体温,持续时间为2h.结论AVPV1阻断剂可以明显阻断CHP的降温效应,但对CHP的发热相无明显影响,提示AVP在CHP引起的降温过程中有重要作用.同时也证明内源性AVP在正常体温中可能有负调节作用.     

Distribution of vasopressin and oxytocin binding sites in the brain and upper spinal cord of the common marmoset

The aim of this study was to label selectively and to map central vasopressin (AVP) and oxytocin (OT) binding sites in the common marmoset. [¹²⁵I]VPA, a compound selective in rodents and human for the AVP V_1a receptor, yielded the same labeling pattern as [³H]AVP, thus suggesting that most AVP receptors present in the marmoset brain are of the V_1a subtype. Numerous areas exhibited AVP binding sites, among which the olfactory bulb, the accumbens nucleus, the bed nucleus of the stria terminalis, the hypothalamic suprachiasmatic, arcuate and ventromedial nuclei, the medial amygdaloid nucleus, the nucleus of the solitary tract and the cerebral cortex. Binding sites for [¹²⁵I]OTA, a selective OT receptor antagonist in rat and human, were markedly less abundant than [¹²⁵I]VPA ones, and, to a few exceptions, expressed in different areas. Neither AVP, nor OT binding sites were detected in the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei identified by neurophysin immunoreactivity. Marked species-related differences were observed in the distribution of both AVP and OT binding sites. Altogether, our data provide a morphological basis to investigate the function of central AVP and OT in the marmoset.     

The pressor effect of angiotensin-(1-7) in the rat rostral ventrolateral medulla involves multiple peripheral mechanisms

OBJECTIVE:

In the present study, the peripheral mechanism that mediates the pressor effect of angiotensin-(1-7) in the rostral ventrolateral medulla was investigated.

METHOD:

Angiotensin-(1-7) (25 pmol) was bilaterally microinjected in the rostral ventrolateral medulla near the ventral surface in urethane-anesthetized male Wistar rats that were untreated or treated (intravenously) with effective doses of selective autonomic receptor antagonists (atenolol, prazosin, methyl-atropine, and hexamethonium) or a vasopressin V₁ receptor antagonist [d(CH₂)₅ -Tyr(Me)–AVP] given alone or in combination.

RESULTS:

Unexpectedly, the pressor response produced by angiotensin-(1-7) (16±2 mmHg, n = 12), which was not associated with significant changes in heart rate, was not significantly altered by peripheral treatment with prazosin, the vasopressin V₁ receptor antagonist, hexamethonium or methyl-atropine. Similar results were obtained in experiments that tested the association of prazosin and atenolol; methyl-atropine and the vasopressin V₁ antagonist or methyl-atropine and prazosin. Peripheral treatment with the combination of prazosin, atenolol and the vasopressin V₁ antagonist abolished the pressor effect of glutamate; however, this treatment produced only a small decrease in the pressor effect of angiotensin-(1-7) at the rostral ventrolateral medulla. The combination of hexamethonium with the vasopressin V₁ receptor antagonist or the combination of prazosin, atenolol, the vasopressin V₁ receptor antagonist and methyl-atropine was effective in blocking the effect of angiotensin-(1-7) at the rostral ventrolateral medulla.

CONCLUSION:

These results indicate that angiotensin-(1-7) triggers a complex pressor response at the rostral ventrolateral medulla that involves an increase in sympathetic tonus, release of vasopressin and possibly the inhibition of a vasodilatory mechanism.     

The effect of AVP‐V1 receptor stimulation on local GFR in the rat kidney

Aim: Arginine vasopressin (AVP) might influence urinary concentration ability by altering the intrarenal distribution of glomerular filtration rate (GFR). Methods: To study this possibility we have measured the intracortical distribution of GFR following acute AVP‐V₁ receptor stimulation in anaesthetized female Sprague–Dawley (SPD) rats during euvolemia and water diuresis by the aprotinin method, allowing two consecutive measurements of zonal GFR in the same kidney. Results: Acute i.v. bolus injection of 50 ng V₁ receptor agonist ([Phe², Ile³, Orn⁸]‐vasopressin) followed by a continuous infusion of 5 ng min^?1 in euvolemic rats reduced GFR by 25% in outer cortex (OC), 20% in middle cortex (MC) and 19% in inner cortex (IC) relative to vehicle infusion (all P < 0.05). In water diuretic rats V₁ receptor agonist reduced GFR by 22% in OC, 10% in MC and 11% in IC relative to vehicle infusion (P < 0.05). GFR decreased slightly more in OC than in MC and IC in both euvolemic and water diuretic rats (P < 0.05) indicating a distribution of GFR towards MC and IC. Acute infusion of the selective non‐peptide V₁ receptor antagonist OPC‐21268 in euvolemic rats reduced GFR by 14% in OC, 13% in MC and 11% in IC relative to vehicle infusion (P < 0.05), with no significant difference between the layers. Conclusions: The change in distribution of GFR not only between OC and IC, but also between OC and MC suggests that the afferent/efferent arterioles and not the medullary vasa recta is the main site of resistance change. We conclude that acute i.v. infusion of V₁ receptor agonist in high doses reduces GFR more in superficial than in deep cortex in both euvolemic and water diuretic rats and that this may be of some importance for water conservation, adding to the V₂‐ receptor effect on water permeability of the collecting ducts.     

[Arginine]vasopressin hydrolyses phosphoinositides in the medullary thick ascending limb of mouse nephron

NaCl reabsorption across the thick ascending limb of Henle's loop (TAL) is stimulated by several hormones, in particular vasopressin acting through V₂ receptors and cyclic AMP production. This study used suspensions of medullary TAL (mTAL) tubules from the mouse nephron to investigate the possibility that, besides activating adenylyl cyclase, vasopressin also stimulates phospholipase C via V₁ receptor occupancy. Two different methods, phosphoinositide labelling and inositol trisphosphate (InsP ₃) radioimmunoassay, were used to show that [arginine]vasopressin (AVP) rapidly stimulated the formation of InsP ₃, which peaked at 200%–250% of control within the first minute of incubation with 10 nmol/l vasopressin at 37°C, and declined to basal level after 5–10 min. Dose/response curves for InsP ₃, established at 30°C and 37° C using radioimmunoassay, showed a half-maximal stimulation of InsP ₃ production at about 1 nmol/l AVP and a maximal response at 10 nmol/l. Similar values were obtained for the response to AVP in terms of cAMP accumulation. InsP ₃ content in the presence of higher concentrations of AVP (1 mol/l) was significantly lower (P<0.001) than in the presence of 10 nmol/l AVP, giving a bell-shaped appearance to the dose/response curve at 37° C but not at 30° C. The V₂ receptor agonist, 1-deamino-[8DArg]vasopressin (dAVP) did not stimulate the formation of InsP ₃, and the V₁ receptor antagonist d(CH₂)₅[Tyr(Me)²]AVP inhibited AVP-induced InsP ₃ formation, which therefore appeared to be mediated by V₁ receptor occupancy. Under the same conditions, AVP also induced the formation of diradylglycerol via V₁ receptor activation, with an analogous dose/response curve. These results show that AVP, in addition to its well-known action through V₂ receptors, also acts on the mouse mTAL through a V₁-mediated stimulation of phospholipase C. Cyclic AMP controls this transduction pathway: dAVP (10 nmol/l), dibutyryl-cAMP (1 mmol/l and 0.1 mmol/l) and forskolin (1 mol/l) decreased the InsP ₃ formation induced by AVP. Dibutyryl-cAMP itself at 37°C also reduced the diglyceride content.     

Effects of receptor blockade on metabolism and renal actions of vasopressin in conscious dogs

Vasopressin – but not the V₂ receptor agonist [deamino-cis1,D-Arg8]-vasopressin (dDAVP) – may mediate natriuresis in dogs. The present study investigated this phenomenon by use of nonpeptide antagonists to V_1a and V₂ receptors 1-{1-[4- (3-acetylaminopropoxy)benzoyl]-4-piperidyl}-3,4-dihydro-2 (1H)-quinolinone (OPC-21268) and 5-dimethylamino-1-{4- (2-methylbenzoylamino)-benzoyl}-2,3,4,5-tetrahydro-1H-benzazepine (OPC-31260), respectively) hypothesising that only V_1a inhibition would reduce the natriuresis. In conscious dogs vasopressin secretion was suppressed by water loading (2% body weight) and replaced by infusion of vasopressin (50 pg min^?1 kg^?1) resulting in physiological plasma concentrations (plasma levels of AVP (pAVP) = 2.0 ± 0.1 pg mL^?1). In this setting, OPC-21268 did not change the rate of sodium excretion. OPC-31260 increased water excretion 12-fold without significant changes in sodium excretion. Heart rate, mean arterial blood pressure, glomerular filtration rate, and clearance of endogenous Li⁺ were unchanged. During vasopressin infusion, both antagonists increased pAVP, OPC-21268 by 20% and OPC-31260 by 100% (2.0 ± 0.2–4.0 ± 0.3 pg mL^?1). In the absence of vasopressin infusion, OPC-31260 did not increase pAVP. Thus, the increase in pAVP appeared to be due to a decrease in metabolic clearance rate. The results indicate that the present dose of V_1a receptor inhibitor OPC-21268 does not reduce sodium excretion and that both vasopressin antagonists inhibit vasopressin metabolism.     

Febrile effects of polyriboinosinic acid: polyribocytidylic acid and interferon: relationship to somatostatin in rat hypothalamus

The changes in thermoregulatory effectors produced by an injection of polyriboinosinic acid: polyribocytidylic acid (Poly I:C) or interferon were assessed and compared in control rats, in rats with hypothalamic somatostatin (SS) receptor blockade and in rats with hypothalamic SS depletion. Intrahypothalamic (i.h., 0.05–0.50 μg) or intraperitoneal (i.p., 100–600 μg) administration of Poly I:C caused a dose-related rise in colon temperature in control rats at all ambient temperatures (T_a) studied. A Poly I:C-induced fever was produced by increased metabolism at a T_a of 8 °C, whereas at 30 °C, it was caused by cutaneous vasoconstriction. At a T_a of 22 °C, the fever was caused by increased metabolism and cutaneous vasoconstriction. On the other hand, i.h. administration of SS-14 antagonist (0.1–0.5 ng) caused a dose-related fall in colon temperature at T_a of 8 °C or 22 °C. At a T_a of 8 °C, the hypothermia was caused by decreased metabolism, whereas at 22 °C, it was caused by decreased metabolism and cutaneous vasodilation. At a T_a of 30 °C, the thermoregulatory effectors were not affected by SS-14 antagonist treatment. Furthermore, the fever induced by Poly I:C or interferon was significantly reduced by pretreatment of rats with an i.p. dose of cysteamine (30 mg. kg⁻¹) or an i.h. dose of SS-14 antagonist (0.1 ng). The results indicate that a somatostatinergic pathway in rat hypothalamus may mediate the fever induced by interferon or its inducer Poly I:C.