三七绒根中皂甙B1及B2的分离和鉴定

从三七Panax notoginseng(Burk.)F.H.Chen绒根中分得二种微量皂甙,三七皂甙B₁和B₂三七皂甙B₁为一种新皂甙,证明其结构为达玛20(22)-烯3β,12β,25三醇6-O-β-D-葡萄吡喃糖甙(Ⅰ),其皂甙元亦为一种新皂甙元,其结构为达玛20(22)-烯-3β,12β,6 C,25四醇。三七皂甙B₂经鉴定为已知皂甙人参皂甙(ginsenoside—Rh₁,Ⅱ)。     

3-甲基芬太尼衍生物QSAR研究

用Hansch途径研究了一系列3-甲基芬太尼衍生物理化性质与镇痛活性间的关系。初步结果表明,镇痛活性与化合物的油/水分配系数之间无规律性变化;与R_2取代基的立体效应(如L,B_1～B_4及MR_(R2))和疏水常数(π_(R2))间有一定的匹配关系,与R_3取代基的Hammen常数(σ)呈抛物线型。引入1-β羟基亦颇为有利。从作用机理推测,该类衍生物的R_2和■可能是与受体相结合的基团,R_1可能仅起药物转运的载体作用,1-β羟基也可能通过氢键参与与受体的互补部位缔合。     

强效镇痛剂研究——Ⅴ.N-[1-(β-羟基-β-苯乙基)-3-甲基-4-哌啶基]-N-丙酰苯胺(7302)酯类衍生物的合成及镇痛活性

本文报道了一系列N-[1-(β-酰氧基-β-苯乙基)-3-甲基-4-哌啶基]-N-丙酰苯胺类衍生物及其化学结构与镇痛强度之间的关系,并测定了几个代表化合物的镇痛作用时间及与阿片受体亲和力。实验结果表明,7302的β-羟基酯化后,均能维持一定的镇痛强度,其镇痛作用时间与母体化合物7302相近。从受体结合试验来看,酯化后与受体亲和的能力显著下降。     

强效镇痛剂研究 Ⅶ.1-β-羟基-3-甲基芬太尼(7302)及有关化合物非对映异构体的合成及镇痛活性

本文报道N-[1-(β-羟基-β-苯乙基)-3-甲基-4-哌啶基]-N-丙酰苯胺(简称1-β-羟基-3-甲基芬太尼,编号7302)及N-[1-苯甲酰基甲基-3-甲基-4-哌啶基]-N-丙酰苯胺(7303)非对映异构体的合成及镇痛活性。初步结果表明(小鼠,ip,热板法),7302分子中三个手性中心的构型对镇痛活性影响都至关重要。顺-A-7302的强度为顺-B-7302的5.3倍,反-A-7302为反-B-7302的2倍左右。顺-A-7302为四个非对映异构体中作用最强者,为吗啡的6000多倍,为依托芬的3倍左右。     

朝鲜淫羊藿的化学成分

从朝鲜淫羊藿(Epimedium koreanum Na kai)的地上部分分离出3个新化合物,应用化学和波谱分析方法,其结构分别确定为3-O-β-D-吡喃葡萄糖(1→3)-α-L-(4-乙酰基)吡喃鼠李糖-脱水淫羊藿素-7-O-β-D-吡喃葡萄糖苷(1),2-(对-羟基苯氧)-5,7-二羟基-6-异戊烯基色酮(2),7-羟基-3,4,6-三甲氧基-9,10-二氢菲-2-O-β-D-吡喃葡萄糖苷(3)。化合物1和3分别命名为朝藿苷丙(korepimedoside C)和淫羊藿苷A₇(icarisideA₇)。     

脑5-HT1A/1B、α2受体及腺苷酸环化酶参与了胍丁胺的抗抑郁作用

为了在单胺受体及受体后腺苷酸环化酶(adenylate cyclase,AC)水平探讨胍丁胺(agmatine,AGM)抗抑郁作用的精细机制,采用小鼠悬尾实验和强迫游泳实验观察AGM抗抑郁行为改变。采用放射免疫方法测定大鼠前额皮层突触膜蛋白AC活性。结果表明,AGM(5～40 mg·kg^-1,ig)在小鼠悬尾实验和强迫游泳实验模型上均有显著抗抑郁活性。同时伍用β受体/5-HT_1A/1B受体阻断剂吲哚洛尔(pindolol, PIN, 20 mg·kg^-1, ip)、 α₂肾上腺素受体拮抗剂育亨宾(yohimbine, YOH, 5～10 mg·kg^-1, ip)或咪唑克生(idazoxan, IDA, 4 mg·kg^-1, ip)对AGM(40 mg·kg^-1, ig)的抗抑郁活性具有显著拮抗效应; 而β受体阻断剂普萘洛尔(propranolol, PRO, 5～20 mg·kg^-1, ip)或5-HT₃受体拮抗剂曲匹西隆(tropisetron, TRO, 5～40 mg·kg^-1, ip)对AGM(40 mg·kg^-1, ig)的抗抑郁活性无显著影响。AGM(0.1～6.4 μmol·L^-1)与大鼠前额皮层提取的突触膜共孵可剂量依赖地激活AC活性, 而PIN(1 μmol·L^-1)或YOH(0.25～1 μmol·L^-1)均显著拮抗AGM(6.4 μmol·L^-1)对AC的激活作用; 慢性给予大鼠AGM(10 mg·kg^-1, ig, bid)或氟西汀(fluoxetine, FLU, 10 mg·kg^-1, ig, bid) 2 w也显著增强大鼠前额皮层基础及Gpp(NH)p 预激活的AC活性。本研究表明, 调节脑内5-HT_1A/1B和α₂等受体功能, 并激活前额皮层AC可能是AGM抗抑郁活性的重要机制之一。     

卡尔曼滤波分光光度法测定复方维生素B片四组分含量

复方维生素B片中的主要成分维生素B₁,B₂,B₆及烟酰胺各具有一定的不稳定性,且配方比例差较大,因而给多组分同时测定带来一定的困难。本文研究了应用卡尔曼滤波分光光度法同时测定复方维生素B片中的主要成分的可行性,并在处理由于分子间的相互作用引起的吸收度偏离Beer-Lambert定律的现象作了探索,得到较满意的结果。维生素B₁,B₂,B₆及烟酰胺的回收率分别是:100.2±0.90%(CV),100.3±1.7%(CV),101.1±3.3%(CV),99.90±0.65%(CV)。较已有的报道结果均好,表明方法可行。     

构树叶的化学成分

为研究构树叶(Broussonetia papyrifera)的化学成分，用Diaion HP-20，Toyopearl HW-40C，Sephadex LH-20，silica gel等柱色谱方法进行分离，根据其理化性质和波谱数据鉴定化合物结构。分离得到了19个化合物，分别鉴定为芹菜素(1)，芹菜素-7-O-β-D-吡喃葡糖苷(2)，柯伊利素-7-O-β-D-吡喃葡糖苷(3)，芹菜素-7-O-β-D-吡喃葡糖醛酸苷(4)，牡荆素-7-O-β-D-吡喃葡糖苷(5)，木犀草素(6)，5,7,4′-三羟基-6-C-［a-L-鼠李糖(1→2)］-β-D-葡糖黄酮碳苷(7)，5,7,4′-三羟基-8-C-［α-L-鼠李糖(1→2)］-β-D-葡糖黄酮碳苷(8)，异牡荆素(9)，牡荆素(10)，苯甲酸苯甲酯-2,6-二-O-β-D-吡喃葡糖苷(11)，(2R,3R,5R,6S,9R)-3-羟基-5,6-环氧-β-紫罗兰醇-2-O-β-D-葡糖苷(12)，(2R,3R,5R,6S,9R)-3-羟基-5,6-环氧-乙酰-β-紫罗兰醇-2-O-β-D-葡糖苷(13)，ficustriol (14)，(6S,9S)-玫瑰花苷(15)，3β-羟基-5α,6α-环氧-β-紫罗兰酮-2α-O-β-D-葡糖苷(16)，icariside B₁ (17)，sammangaoside A (18)，3-羟基-5α,6α-环氧-β-紫罗兰酮(19)。化合物11、12、13为新化合物，其余化合物为首次从该属植物中分离得到。     

HPLC法同时测定复方三维右旋泛酸钙糖浆中4中维生素的含量

目的 建立高效液相色谱(HPLC)法同时测定复方三维右旋泛酸钙糖浆中维生素B₁、维生素B₂、维生素B₆和烟酰胺的含量。方法 采用外标法进行测定,色谱柱为Thermo Betasil C₁₈ Analytical(4.6 mm×250 mm, 5 μm),流动相为乙腈-5 mmol·L^-1十二烷基硫酸钠（含0.05%甲酸）水溶液梯度洗脱,流速1.0 mL·min^-1,检测波长260 nm,柱温30 ℃。分别测定10批复方三维右旋泛酸钙糖浆。结果 维生素B₁、维生素B₂、维生素B₆、烟酰胺4种成分的线性范围分别为5.76~115.2 μg·mL^-1(r=0.999 9)、1.16~23.20 μg·mL^-1(r=0.999 9)、1.72~34.4 μg·mL^-1(r=0.999 6)和5.76~115.2 μg·mL^-1(r=0.999 9),平均加样回收率为96.2%~98.4%(RSD为2.14%~3.42%)。不同批次复方三维右旋泛酸钙糖浆中维生素B₁、维生素B₂、维生素B₆、烟酰胺含量范围分别为0.133 7~0.155 9、0.027 86~0.030 71、0.039 05~0.047 7、0.138 7~0.148 2 mg·g^-1。结论 该方法为完善复方三维右旋泛酸钙糖浆的质量标准和加强质量控制提供了新的方法和依据。     

拟人参皂苷F11在大鼠体内的药物代谢研究

目的探讨拟人参皂苷F11在大鼠体内的药物代谢产物及其过程.方法ip拟人参皂苷F₁₁后,应用TLC分析排泄物中的代谢产物,并利用制备薄层分离制备代谢产物,通过波谱解析(MS,¹HNMR,¹³CNMR,¹H-¹HCOSY)确定其结构.结果从粪便中分离鉴定了3种代谢产物,分别为拟人参皂苷R_T5,ocotillol和1个新的代谢产物F-3-1,并确定其结构为6-O-α-L-吡喃鼠李糖基(1-2)-β-D-吡喃葡糖基-(20S,23S,24R)-达玛-20(24)-环氧-3β,6α,12β,23,25-五醇(6-O-α-L-rhamnopyranosyl-(1-2)-β-D-glucopyranosyl-(20S,23S,24R)-dammar-20(24)-epoxy-3-β,6α,12β,23,25-pentanol).但在尿液和胆汁中并未发现任何代谢产物.结论拟人参皂苷F₁₁不被肝脏代谢,但胆汁排泄物可在肠道被代谢为水解和氧化产物.     

Characterization of the cloned guinea pig leukotriene B4 receptor: comparison to its human orthologue

A cDNA clone coding for the guinea pig leukotriene B₄ (BLT) receptor has been isolated from a lung cDNA library. The guinea pig BLT receptor has an open reading frame corresponding to 348 amino acids and shares 73% and 70% identity with human and mouse BLT receptors, respectively. Scatchard analysis of membranes prepared from guinea pig and human BLT receptor-transfected human embryonic kidney (HEK) 293 EBNA (Epstein–Bar Virus Nuclear Antigen) cells showed that both receptors displayed high affinity for leukotriene B₄ (K_d value of 0.4 nM) and were expressed at high levels (B_max values ranging from 9 to 12 pmol/mg protein). The rank order of potency for leukotrienes and related analogs in competition for [³H]leukotriene B₄ specific binding at the recombinant guinea pig BLT receptor is leukotriene B₄>20-OH-leukotriene B₄>12(R)-HETE ((5Z,8Z,10E,12(R)14Z)-12-hydroxyeicosatetraen-1-oic acid)>12(S)-HETE ((5Z,8Z,10E,12(S)14Z)-12-Hydroxyeicosatetraen-1-oic acid)>20-COOH-leukotriene B₄>U75302 (6-(6-(3-hydroxy-1E,5Z-undecadienyl)-2-pyridinyl)-1,5-hexanediol)leukotriene C₄=leukotriene D₄=leukotriene E₄. For the human receptor the rank order of 12(S)-HETE, 20-COOH-leukotriene B₄ and U75302 was reversed. Xenopus melanophore and HEK aequorin-based reporter gene assays were used to demonstrate that the guinea pig and human BLT receptors can couple to both the cAMP inhibitory and intracellular Ca²⁺ mobilization signaling pathways. However, in the case of the aequorin-expressing HEK cells (designated AEQ17-293) transfected with either the guinea pig or human BLT receptor, expression of G_α16 was required to achieve a robust Ca²⁺ driven response. Leukotriene B₄ was a potent agonist in functional assays of both the guinea pig and human BLT receptors. U-75302 a leukotriene B₄ analogue which possesses both agonistic and antagonistic properties behaved as a full agonist of the guinea pig and human BLT receptors in AEQ17-293 cells and not as an antagonist. The recombinant guinea pig BLT receptor will permit the comparison of the intrinsic potencies of leukotriene B₄ receptor antagonists used in guinea pig in vivo models of allergic and inflammatory disorders.     

Adenosine receptor subtype-selective antagonists in inflammation and hyperalgesia

In this study, we examined the effects of systemic and local administration of the subtype-selective adenosine receptor antagonists PSB-36, PSB-1115, MSX-3, and PSB-10 on inflammation and inflammatory hyperalgesia. Pharmacological blockade of adenosine receptor subtypes after systemic application of antagonists generally led to a decreased edema formation after formalin injection and, with the exception of A₃ receptor antagonism, also after the carrageenan injection. The selective A_2B receptor antagonist PSB-1115 showed a biphasic, dose-dependent effect in the carrageenan test, increasing edema formation at lower doses and reducing it at a high dose. A₁ and A_2B antagonists diminished pain-related behaviors in the first phase of the formalin test, while the second, inflammatory phase was attenuated by A_2B and A₃ antagonists. The A_2B antagonist was particularly potent in reducing inflammatory pain dose-dependently reaching the maximum effect at a low dose of 3 mg/kg. Inflammatory hyperalgesia was totally eliminated by the A_2A antagonist MSX-3 at a dose of 10 mg/kg. In contrast to the A₁ antagonist, the selective antagonists of A_2A, A_2B, and A₃ receptors were also active upon local administration. Our results demonstrate that the blockade of adenosine receptor subtypes can decrease the magnitude of inflammatory responses. Selective A_2A antagonists may be useful for the treatment of inflammatory hyperalgesia, while A_2B antagonists have potential as analgesic drugs for the treatment of inflammatory pain.     

The role of kinin B1 and B2 receptors in the scratching behaviour induced by proteinase-activated receptor-2 agonists in mice

Background and purpose:

Activation of the proteinase-activated receptor-2 (PAR-2) induces scratching behaviour in mice. Here, we have investigated the role of kinin B₁ and B₂ receptors in the pruritogenic response elicited by activators of PAR-2.

Experimental approach:

Scratching was induced by an intradermal (i.d.) injection of trypsin or the selective PAR-2 activating peptide SLIGRL-NH₂ at the back of the mouse neck. The animals were observed for 40 min and their scratching response was quantified.

Key results:

I.d. injection of trypsin or SLIGRL-NH₂ evoked a scratching behaviour, dependent on PAR-2 activation. Mice genetically deficient in kinin B₁ or B₂ receptors exhibited reduced scratching behaviour after i.d. injection of trypsin or SLIGRL-NH₂. Treatment (i.p.) with the non-peptide B₁ or B₂receptor antagonists SSR240612 and {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657, respectively, prevented the scratching behaviour caused by trypsin or SLIGRL-NH₂. Nonetheless, only treatment i.p. with the peptide B₂receptor antagonist, Hoe 140, but not the B₁receptor antagonist (DALBK), inhibited the pruritogenic response to trypsin. Hoe 140 was also effective against SLIGRL-NH₂-induced scratching behaviour when injected by i.d. or intrathecal (i.t.) routes. Also, the response to SLIGRL-NH₂ was inhibited by i.t. (but not by i.d.) treatment with DALBK. Conversely, neither Hoe 140 nor DALBK were able to inhibit SLIGRL-NH₂-induced scratching behaviour when given intracerebroventricularly (i.c.v.).

Conclusions and implications:

The present results demonstrated that kinins acting on both B₁ and B₂ receptors played a crucial role in controlling the pruriceptive signalling triggered by PAR-2 activation in mice.     

Inflammatory muscle pain is dependent on the activation of kinin B₁ and B₂ receptors and intracellular kinase pathways

BACKGROUND AND PURPOSE

B₁ and B₂ kinin receptors are involved in pain transmission but they may have different roles in the muscle pain induced by intense exercise or inflammation. We investigated the contribution of each of these receptors, and the intracellular pathways involved, in the initial development and maintenance of the muscle pain associated with inflammation-induced tissue damage.

EXPERIMENTAL APPROACH

Mechanical hyperalgesia was measured using the Randall–Selitto apparatus after injecting 5% formalin solution into the gastrocnemius muscle in mice treated with selective antagonists for B₁ or B₂ receptors. The expression of kinin receptors and cytokines and the activation of intracellular kinases were monitored by real-time PCR and immunohistochemistry.

KEY RESULTS

The i.m. injection of formalin induced an overexpression of B₁ and B₂ receptors. This overexpression was associated with the mechanical hyperalgesia induced by formalin because treatment with B₁ receptor antagonists (des-Arg⁹[Leu⁸]-BK, DALBK, and SSR240612) or B₂ receptor antagonists (HOE 140 and {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657) prevented the hyperalgesia. Formalin increased myeloperoxidase activity, and up-regulated TNF-α, IL-1β and IL-6 in gastrocnemius. Myeloperoxidase activity and TNF-α mRNA expression were inhibited by either DALBK or HOE 140, whereas IL-6 was inhibited only by HOE 140. The hyperalgesia induced by i.m. formalin was dependent on the activation of intracellular MAPKs p38, JNK and PKC.

CONCLUSIONS AND IMPLICATIONS

Inflammatory muscle pain involves a cascade of events that is dependent on the activation of PKC, p38 and JNK, and the synthesis of IL-1β, TNF-α and IL-6 associated with the up-regulation of both B₁ and B₂ kinin receptors.     

Effects of kinin B1 and B2 receptor antagonists on overactive urinary bladder syndrome induced by spinal cord injury in rats

Background and Purpose

Kinin B₁ and B₂ receptors have been implicated in physiological and pathological conditions of the urinary bladder. However, their role in overactive urinary bladder (OAB) syndrome following spinal cord injury (SCI) remains elusive.

Experimental Approach

We investigated the role of kinin B₁ and B₂ receptors in OAB after SCI in rats.

Key Results

SCI was associated with a marked inflammatory response and functional changes in the urinary bladder. SCI resulted in an up-regulation of B₁ receptor mRNA in the urinary bladder, dorsal root ganglion and spinal cord, as well as in B₁ protein in the urinary bladder and B₁ and B₂ receptor protein in spinal cord. Interestingly, both B₁ and B₂ protein expression were similarly distributed in detrusor muscle and urothelium of animals with SCI. In vitro stimulation of urinary bladder with the selective B₁ or B₂ agonist elicited a higher concentration-response curve in the SCI urinary bladder than in naive or sham urinary bladders. Cystometry revealed that treatment of SCI animals with the B₂ selective antagonist icatibant reduced the amplitude and number of non-voiding contractions (NVCs). The B₁ antagonist des-Arg⁹-[Leu⁸]-bradykinin reduced the number of NVCs while the non-peptide B₁ antagonist SSR240612 reduced the number of NVCs, the urinary bladder capacity and increased the voiding efficiency and voided volume.

Conclusions and Implications

Taken together, these data show the important roles of B₁ and B₂ receptors in OAB following SCI in rats and suggest that blockade of these receptors could be a potential therapeutic target for controlling OAB.     

Evidence for the participation of kinins in Freund's adjuvant-induced inflammatory and nociceptive responses in kinin B1 and B2 receptor knockout mice

Experiments were designed to investigate the role of kinin B₁ and B₂ receptors in Freund's adjuvant (CFA)-induced inflammation and nociception responses by the use of B₁ and B₂ null mutant mice. Intradermal (i.d.) injection of CFA produced time-dependent and marked hyperalgesic responses in both ipsilateral and contralateral paws of wild-type mice. Gene disruption of the kinin B₂ receptor did not interfere with CFA-induced hyperalgesia, but ablation of the gene of the B₁ receptor reduced the hyperalgesia in both ipsilateral (48±13%, at 12 h) and contralateral (91±22%, at 12 h) paws. Treatment of wild-type mice with the selective B₁ antagonist des-Arg⁹-[Leu⁸]-BK (150 nmol/kg, s.c.) reduced CFA-evoked thermal hyperalgesia, to an extent which was similar to that observed in mice lacking kinin B₁ receptor. I.d. injection of CFA produced a time-related and long-lasting (up to 72 h) increase in paw volume in wild-type mice. A similar effect was observed in B₁ knockout mice. In mice lacking B₂ receptor, the earlier stage of the CFA-induced paw oedema (6 h) was significantly greater compared with the wild-type animals, an effect which was almost completely reversed (76±5%) by des-Arg⁹-[Leu⁸]-BK. This data demonstrates that kinin B₁ receptor, but not B₂ receptor, exerts a critical role in controlling the persistent inflammatory hyperalgesia induced by CFA in mice, while B₂ receptor appears to have only a minor role in the amplification of the earlier stage of CFA-induced paw oedema formation. The results of the present study, taken together with those of previous studies, suggest that B₁ receptor antagonists represent a potential target for the development of new drugs to treat persistent inflammatory pain.     

The endocannabinoid anandamide inhibits kinin B1 receptor sensitization through cannabinoid CB1 receptor stimulation in human umbilical vein

The possible inhibition of kinin B₁ receptor up-regulation by arachidonoylethanolamide (anandamide) was evaluated in isolated human umbilical vein. Anandamide and its metabolically stable analogue, R-N-(2-Hydroxy-1-methylethyl)-5Z,8Z,11Z,14Z-eicosatetraenamide (R-(+)-methanandamide), produced a selective and dose-dependent inhibition of kinin B₁ receptor-sensitized contractile responses. The inhibitory effect of anandamide on B₁ receptor-sensitized responses failed to be modified either by 5-biphenyl-4-ylmethyl-tetrazole-1-carboxylic acid dimethylamide (LY2183240), a selective anandamide uptake inhibitor, or 6-Iodo-2-methyl-1-[2-(4-morpholinyl)ethyl]-1H-indol-3-y l](4-methoxyphenyl) methanone (AM630), selective cannabinoid CB₂ receptor antagonist. However, the cannabinoid CB₁ receptor antagonist, N-(Piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophen yl)-4-methyl-1H-pyrazole-3-carboxamide (AM251), abolished anandamide effects on kinin B₁ receptor sensitization. The present results provide strong pharmacological evidence indicating that endocannabinoid anandamide inhibits kinin B₁ receptor up-regulation through cannabinoid CB₁ receptor stimulation in human umbilical vein.     

A novel kainate receptor ligand [H]-(2S,4R)-4-methylglutamate: Pharmacological characterization in rabbit brain membranes

Since kainate evokes large non-desensitizing currents at α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, kainate is of limited use in discriminating between AMPA and kainate receptors. Following recent reports that (2S,4R)-4-methylglutamate is a kainate receptor-selective agonist, we have radiolabelled and subsequently characterized the binding of [³H]-(2S,4R)-4-methylglutamate to rabbit whole-brain membranes. [³H]-(2S,4R)-4-methylglutamate binding was rapid, reversible and labelled two sites (KD1 = 3.67 ± 0.50 nM/B_max1 = 0.54 ± 0.03 pmol/mg protein and K_D2 = 281.66 ± 12.33 nM/ B_max2 = 1.77 ± 0.09 pmol/mg protein). [³H]-(2S,4R)-4-methylglutamate binding was displaced by several non-NMDA receptor ligands: domoate > kainate -quisqualate -glutamate > 6-cyano-7-nitroquinoxaline-2, 3-dione (CNQX) (S)-AMPA = (S)-5-fluorowillardiine > NMDA. Neither the metabotropic glutamate receptor agonists (1S,3R)-ACPD or -AP4, together with the -glutamate uptake inhibitor -trans-2,4-PDC, influenced binding when tested at 100 μM. We conclude that [³H]-(2S,4R)-4-methylglutamate is a useful radioligand for labelling kainate receptors. It possesses high selectivity, and possesses a pharmacology similar to that for rat cloned low-affinity (Glu5 and 6) kainate receptor subunits.