N-methyl-D-aspartate injection into the massa intermedia facilitates development of limbic kindling in rats.

The effect on limbic kindling of N-methyl-D-aspartate (NMDA) injection into the midline thalamus of rats was investigated. Repeated injection of 25 nmol/0.5 microliters NMDA (experimental group) into the massa intermedia (MI), particularly into the reuniens nucleus, caused tonic and/or clonic generalized convulsion associated with temporal limbic EEG seizure discharge. This did not occur after injection of phosphate-buffered saline (PBS, control group). When the animals were subjected to subsequent kindling at either the hippocampus (HP) or the amygdala (AM), only the experimental group showed a significant facilitation of kindling rate. The results suggest that an NMDA receptor in the reuniens nucleus participates in modulation of temporal limbic excitability and seizure development.     

Selective blockade of dopamine D-1 receptors by SCH 23390 discloses striatal dopamine D-2 receptors mediating the inhibition of adenylate cyclase in rats

l-Glutamate but not methyl-D-aspartate (NMDA) or quisqualate (Quis) (10^?6 M) in vitro with or without preincubation increased significantly the K_D value of the [³H]N-propylnorapomorphine ([³H]NPA) binding sites by 21 and 36% respectively in striatal membranes of rat without influencing the striatal [³H]spiperone binding sites. The number of striatal [³H]NPA binding sites was not changed by l-glutamate (10^?6 and 10^?5 M) in vitro. There may thus exist interactions between striatal glutamate receptors — not related to excitatory amino-acid receptors of the NMDA or the QUIS type - and high affinity striatal DA receptors.     

N-methyl-D-aspartate receptor agonists and antagonists partially affect the duration of ketamine anesthesia in the rat

The effects of intracerebroventricular injection of excitatory amino acids which act on the N-Methyl-D-aspartate (NMDA) receptor complex on the duration of loss of righting reflex (DLRR) induced by intravenous injection to ketamine (20 mg/kg) were investigated in rats. Ketamine-induced DLRR was 10.3 min, but NMDA receptor agonistsd-alanine (200 μg) or NMDA (0.15 μg) did not change DLRR. However,d-alanine combined with NMDA significantly shortened DLRR (7.7 min). The NMDA receptor antagonist 7-chlorokynurenic acid (10 μg) alone prolonged DLRR significantly (16.2 min), but not when combined withd-alanine. These data suggest that NMDA receptor blockade contributes at least partially to the mechanism of ketamine anesthesia.     

帕金森病运动并发症发生机制中G蛋白偶联受体激酶6与N-甲基-D-天冬氨酸受体关系的研究

Objective To investigate the relationship between G protein-coupled receptor kinase 6 (GRK6) and N-methyl-D-aspartate (NMDA) receptor in the mechanism study underlying motor complications in Parkinson's disease (PD).Methods The rat models (n= 25) of Parkinsonism related motor complications were established and were randomly divided into levodopa-induced dyskinesia (LID) group (n= 10,intraperitoneal injection of levodopa for 23 d),MK-801 treatment group (n= 10,intraperitoneal injection of MK-801 at day23 after intraperitoneal injection with levodopa for 22 days) and PD group (n= 5,intraperitoneal injection of vitamin C).Another 5 rats were served as controls (sham-operation group).The behavior changes of rats in MK-801 treatment group were observed,and the expression of GRK6 in the striate of rats was detected by immunohistochemistry and Western blot.Results After the chronic treatment with levodopa methyl ester,PD rats displayed abnormal involuntary movements,which was similar to levodopainduced dyskinesia in PD patients.Immunohistochemistry showed that GRK6-positive cells of lesion side were decreased in LID rats as compared with PD rats [(3.23±0.41 ) × 103 vs.(4.81 ± 1.31 ) ×103,P＜0.01].Rats in MK-801 treatment group displayed the decreased AIM scores and increased peak rotation,and the increased GRK6-positive cells of lesion side as compared with LID rats (P＜0.05).Western blot showed that the levels of GRK6 was 83.7% ±2.1% in PD group (presented as lesion side/unlesion side),76.8% ± 2.2% in LID group and 91.1% ± 2.7% in MK-801 treatment group (intergroups comparison:all P＜0.05).These results were in accordance with the results of immunohistochemistry.Conclusions Antagonist of NMDA receptor can be used to reduce the motor complications in rats.It may be due to increased GRK6 which inhibits the overactivation of glutamic acid receptors.     

Small-volume and rapid extracellular solution exchange around Xenopus oocytes during voltage-clamp recordings

 A novel method for micro extracellular perfusion of Xenopus oocytes has been designed in order to minimise the amount of test solution required for drug applications during two-microelectrode voltage-clamp experiments. Voltage-clamp experiments on oocytes are performed in a glass-covered microbath without continuous perfusion. The microelectrodes access the oocytes via two small openings in the glass cover. Test solutions are applied to a funnel at the chamber inflow and the chamber volume is subsequently exchanged by operating a suction pump connected to the chamber outflow. Only 50 μl of drug- or neurotransmitter-containing solution is required for bath application. In addition, the new ”funnel application technique” enables quick and timed applications of drugs or neurotransmitters to Xenopus oocytes within 200–400 ms. Received: 16 December 1997 / Received after revision and accepted: 11 March 1998     

NMDA receptor antagonist effects,cortical glutamatergic function,and schizophrenia: toward a paradigm shift in medication development

There is an urgent need to improve the pharmacotherapy of schizophrenia despite the introduction of important new medications. New treatment insights may come from appreciating the therapeutic implications of model psychoses. In particular, basic and clinical studies have employed the N-methyl-D-aspartate (NMDA) glutamate receptor antagonist, ketamine, as a probe of NMDA receptor contributions to cognition and behavior. These studies illustrate a translational neuroscience approach for probing mechanistic hypotheses related to the neurobiology and treatment of schizophrenia and other disorders. Two particular pathophysiologic themes associated with schizophrenia, the disturbance of cortical connectivity and the disinhibition of glutamatergic activity may be modeled by the administration of NMDA receptor antagonists. The purpose of this review is to consider the possibility that agents that attenuate these two components of NMDA receptor antagonist response may play complementary roles in the treatment of schizophrenia.     

Development of an automated,GMP compliant FASTlab™ radiosynthesis of [18F]GE-179 for the clinical study of activated NMDA receptors

N-(2-chloro-5-(S-2-[¹⁸F]fluoroethyl)thiophenyl)-N'-(3-thiomethylphenyl)-N'-methylguanidine, ([¹⁸F] GE-179 ), has been identified as a promising positron emission tomography (PET) ligand for the intra-channel phencyclidine (PCP) binding site of the N-methyl-D-aspartate (NMDA) receptor. The radiosynthesis of [¹⁸F] GE-179 has only been performed at low radioactivity levels. However, the manufacture of a GMP compliant product at high radioactivity levels was required for clinical studies. We describe the development of a process using the GE FASTlab™ radiosynthesis platform coupled with HPLC purification. The radiosynthesis is a two-step process, involving the nucleophilic fluorination of ethylene ditosylate, 11 , followed by alkylation to the deprotonated thiol precursor, N-(2-chloro-5-thiophenol)-N'-(3-thiomethylphenyl)-N'-methyl guanidine, 8 . The crude product was purified by semi-preparative HPLC to give the formulated product in an activity yield (AY) of 7 ± 2% (n = 15) with a total synthesis time of 120 minutes. The radioactive concentration (RAC) and radiochemical purity (RCP) were 328 ± 77 MBq/mL and 96.5 ± 1% respectively and the total chemical content was 2 ± 1 μg. The final formulation volume was 14 mL. The previously described radiosynthesis of [¹⁸F] GE-179 was successfully modified to deliver an process on the FASTlab™ that allows the manufacture of a GMP quality product from high starting radioactivitity (up to 80 GBq) and delivers a product suitable for clinical use.     

帕金森病运动并发症发生机制中G蛋白偶联受体激酶6与N-甲基-D-天冬氨酸受体关系的研究

Objective To investigate the relationship between G protein-coupled receptor kinase 6 (GRK6) and N-methyl-D-aspartate (NMDA) receptor in the mechanism study underlying motor complications in Parkinson's disease (PD).Methods The rat models (n= 25) of Parkinsonism related motor complications were established and were randomly divided into levodopa-induced dyskinesia (LID) group (n= 10,intraperitoneal injection of levodopa for 23 d),MK-801 treatment group (n= 10,intraperitoneal injection of MK-801 at day23 after intraperitoneal injection with levodopa for 22 days) and PD group (n= 5,intraperitoneal injection of vitamin C).Another 5 rats were served as controls (sham-operation group).The behavior changes of rats in MK-801 treatment group were observed,and the expression of GRK6 in the striate of rats was detected by immunohistochemistry and Western blot.Results After the chronic treatment with levodopa methyl ester,PD rats displayed abnormal involuntary movements,which was similar to levodopainduced dyskinesia in PD patients.Immunohistochemistry showed that GRK6-positive cells of lesion side were decreased in LID rats as compared with PD rats [(3.23±0.41 ) × 103 vs.(4.81 ± 1.31 ) ×103,P＜0.01].Rats in MK-801 treatment group displayed the decreased AIM scores and increased peak rotation,and the increased GRK6-positive cells of lesion side as compared with LID rats (P＜0.05).Western blot showed that the levels of GRK6 was 83.7% ±2.1% in PD group (presented as lesion side/unlesion side),76.8% ± 2.2% in LID group and 91.1% ± 2.7% in MK-801 treatment group (intergroups comparison:all P＜0.05).These results were in accordance with the results of immunohistochemistry.Conclusions Antagonist of NMDA receptor can be used to reduce the motor complications in rats.It may be due to increased GRK6 which inhibits the overactivation of glutamic acid receptors.     

腹腔注射利多卡因对切口痛大鼠脊髓背角NMDA受体-1表达的影响

目的:探讨腹腔注射利多卡因对切口痛模型大鼠痛觉行为和脊髓背角N-甲基-D-天冬氨酸(NMDA)受体-1(NR1)表达的影响。方法:雄性SD大鼠30只,随机分为5组:正常对照组(A组)、手术切口组(B组)、利多卡因5 mg/kg组(C组)、利多卡因10 mg/kg组(D组)及利多卡因20 mg/kg(E组)。除A组外,其他4组按Brennan法制作趾部切口痛模型。C、D、E三组于切口痛模型制备成功后腹腔注射相应剂量的利多卡因。注射后5 min开始观察5组大鼠痛觉行为的改变,以累计疼痛评分评定痛觉行为。观察1 h后取同侧脊髓,用免疫组化方法观察NR1表达的变化。结果:与A组相比,其余各组大鼠术后累积疼痛评分增加,脊髓背角NR1表达增强,差异均有统计学意义(P<0.01)。与B组相比,D组和E组大鼠的累积疼痛评分减少,脊髓背角NR1表达降低,差异均有统计学意义(P<0.05)。结论:腹腔注射利多卡因对切口痛大鼠具有较好的镇痛效果,并抑制其脊髓背角NR1的表达,提示其镇痛机制可能是通过抑制NR1的表达而实现的。