Role of peripheral group I and II metabotropic glutamate receptors in IL-1beta-induced mechanical allodynia in the orofacial area of conscious rats

The present study investigated the role of peripheral group I and II metabotropic glutamate receptors (mGluRs) in interleukin-1beta (IL-1beta)-induced mechanical allodynia in the orofacial area. Experiments were carried out on Sprague-Dawley rats weighing between 230 and 280 g. After subcutaneous administration of 0.01, 0.1, 1, or 10 pg of IL-1beta, we examined withdrawal behavioral responses produced by 10 successive trials of a ramp of air-puffs pressure applied ipsilaterally or contralaterally to the IL-1beta injection site. The thresholds of air puffs were measured 10, 30, 60, 120, or 180 min after 25 microl of IL-1beta was administered through an implanted tube. Subcutaneous injection of IL-1beta produced bilateral mechanical allodynia. While the IL-1beta-induced mechanical allodynia was blocked by pretreatment with an IL-1 receptor antagonist, the IL-1beta-induced mirror-image mechanical allodynia was not blocked by an IL-1 receptor antagonist injected into the contralateral side. Subcutaneous administration of CPCCOEt or LY367385, an mGluR1 antagonist, or MPEP or SIB1893, an mGluR5 antagonist, 10 min prior to injection of IL-1beta abolished IL-1beta-induced mechanical allodynia. Pretreatment with APDC or DCG4, a group II mGluR agonist, blocked the IL-1beta-induced mechanical allodynia. The anti-allodynic effect induced by APDC was inhibited by pretreatment with LY341495, a group II mGluR antagonist. These results suggest that peripheral group I and II mGluRs participate in IL-1beta-induced mechanical allodynia in the orofacial area. Peripheral group I mGluR antagonists blocked the IL-1beta-induced mechanical allodynia, while peripheral group II mGluR agonists produced anti-allodynic effects on IL-1beta-induced mechanical allodynia in the orofacial area of rats.     

Group II metabotropic glutamate receptors modulate extracellular glutamate in the nucleus accumbens.

The regulation of extracellular glutamate in the nucleus accumbens by group II metabotropic glutamate receptors (mGluR2/3) was examined in vivo. Stimulation of mGluR2/3 with 2R,4R-4-aminopyrrolidine-2,4-dicarboxylate (APDC) or N-acetylaspartylglutamate reduced extracellular glutamate levels. Conversely, blockade of mGluR2/3 by LY143495 or (RS)-1-amino-5-phosphonoindan-1-carboxylic acid (APICA) increased extracellular glutamate, an effect antagonized by the coadministration of APDC. These effects likely involve both vesicular and nonvesicular glutamate, because the increase in glutamate by APICA or the decrease by APDC was prevented by blocking N-type calcium channels and the release of glutamate after potassium-induced membrane depolarization was antagonized by APDC. In addition, blockade of the cystine-glutamate exchange, a major nonvesicular source of extracellular glutamate, by (S)-4-carboxyphenylglycine blocked the effects induced by either APDC or APICA. However, blockade of Na(+) channels by tetrodotoxin or Na(+)-dependent glutamate transporters by DL-threo-beta-benzyloxyaspartate failed to affect the alterations in extracellular glutamate by APICA or APDC, respectively. Group II mGluRs are G(i)-coupled and coperfusion with the cAMP-dependent protein kinase (PKA) activator Sp-cAMPS blocked the reduction in glutamate by APDC and the PKA inhibitor Rp-cAMPS prevented the elevation in glutamate by APICA. Taken together, these data support three conclusions: 1) group II mGluRs regulate both vesicular and nonvesicular release of glutamate in the nucleus accumbens, 2) there is tonic in vivo stimulation of mGluR2/3 by endogenous glutamate, and 3) modulation of group II mGluRs of extracellular glutamate is Ca(2+)- and PKA-dependent.     

Regulation of locomotor activity by metabotropic glutamate receptors in the nucleus accumbens and ventral tegmental area

Glutamatergic innervation of the ventral tegmental area (VTA) and the nucleus accumbens (NA) regulates locomotor activity. The present study was designed to evaluate the involvement of metabotropic glutamate receptors (mGluRs) in motor activity. Agonists selective for each of the three subgroups of mGluRs were microinjected into the VTA or NA, and motor activity was monitored. The group I agonist (S)-3,5-dihydroxyphenylglycine elicited a dose-dependent elevation in motor activity after microinjection into either the VTA or NA. The effect in the NA was blocked by the mGluR1-specific antagonist 7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxylate ethyl ester. The group II agonist (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine also elicited a short-duration motor activation after microinjection into either structure. The dose response in the VTA was biphasic, and the coadministration of the group II/III-specific antagonist (RS)-alpha-methyl-4-phosphonophenylglycine partially blocked motor activation in both the NA and VTA. Although the group III agonist L-(+)-2-amino-4-phosphonobutyric acid produced a relatively modest behavioral stimulation after microinjection into the NA, it was without effect in the VTA. These data indicate a role for mGluR subgroups in the regulation of motor activity in the VTA and NA.     

Modeling the binding and function of metabotropic glutamate receptors

A mathematical model for the binding and function of metabotropic glutamate receptors was developed, with the aim to gain new insights into the functioning of these complex receptors. These receptors are homodimers, and each subunit is composed of a ligand binding [Venus flytrap (VFT)] domain and a heptahelical domain (HD) responsible for G-protein activation. Our mechanistic model integrates all structural information available so far: the various states of the VFT dimer (open-open, closed-open, and closed-closed), as well as the fact that a single HD is active at a time. To provide the model with parameters with biological meaning, two published experimental studies were reanalyzed. The first one reports a negative cooperativity in agonist binding (J Biol Chem 279:35526-35534, 2004), whereas the other indicates a positive cooperativity in agonist-mediated response (Nat Struct Mol Biol 11:706-713, 2004). The former study allowed us to explain the mechanistic features associated with VFT recognition by agonists and antagonists integrating a negative allosteric interaction for agonist binding. The second study helped us to quantitatively describe the functional dynamics of transduction of the VFT occupation into functional response, confirming a putative positive cooperativity at the level of receptor coupling efficacy. This model will help both to better understand the functioning of these receptors and to characterize the mechanism of action of various types of allosteric modulators. Moreover, this model may be of general utility for oligomeric systems in which the ligand binding and effector domains correspond to distinct structural domains.     

Attenuation of capsaicin-evoked mechanical allodynia by peripheral neuropeptide Y Y1 receptors

Neuropeptide Y (NPY) and its cognate receptors are important modulators of nociception and their expression is significantly altered following injury. In particular, previous studies have demonstrated that the Y1 subtype of NPY receptors inhibits nociceptive transmission from capsaicin-sensitive terminals in the dorsal horn of the spinal cord. The present study evaluated the function of the Y1 receptor on peripheral terminals of primary afferent neurons by testing whether peripherally administered Y1 agonists and antagonists alter capsaicin-evoked mechanical allodynia in rats and capsaicin-evoked immunoreactive calcitonin gene-related peptide (iCGRP) release from isolated superfused rat skin. Treatment with the Y1 agonist [Leu31,Pro34]-NPY (0.5, 1, or 10 nmol) significantly inhibited capsaicin-evoked mechanical allodynia in a dose-dependent manner. This effect was reversible by pretreatment with the Y1 antagonist BIBO3304 (10 nmol). The anti-allodynia produced by the Y1 agonist occurred at a peripheral site of action, because injection into the paw contralateral to the site of the capsaicin injection had no effect on paw withdrawal latencies. In isolated skin, application of [Leu31,Pro34]-NPY (300 nM) significantly inhibited capsaicin-evoked CGRP release. BIBO3304 reversed this inhibition, having itself no effect on capsaicin-evoked iCGRP release. These studies indicate that the activation of peripheral Y1 receptors produces anti-allodynia, possibly via the direct inhibition of capsaicin-sensitive fibers.     

脑缺血耐受中亲代谢型谷氨酸受体1α下调的意义

目的:观察局灶脑缺血预处理对亲代谢型谷氨酸受体1α(metabotropicglutamatereceptor1α,mGluR1α)表达的影响并初步探讨其在脑缺血耐受中的意义。方法:SD大鼠单纯随机分为3组,对照组给予两次假手术,其余两组分别在2h大脑中动脉阻塞(MCAO)及22h再灌注前3d给予10min的预缺血或假手术,比较各组梗死体积、脑组织病理变化及mGluR1α免疫组化染色的平均光密度(MOD)和积分光密度(IOD)。结果:预缺血组梗死体积较假手术组减小53.48%(t=8.896,P=0.0006),神经元变性、坏死亦轻于假手术组,同时伴mGluR1α表达降低(PMOD=0.00021,PIOD=0.00012)。图像分析显示3组间MOD(F=359.496,P=0.00038)及IOD(F=285.167,P=0.00036)差异有显著性意义。结论:10minMCAO可有效诱导缺血耐受,减轻二次缺血所致的神经元死亡,减少mGluR1α表达。mGluR1α表达下调可能是局灶性脑缺血耐受产生的分子机制之一。     

亲代谢型谷氨酸受体配基对帕金森病大鼠的神经保护作用

目的探讨PD模型大鼠黑质致密部亲代谢型谷氨酸受体(mGluRs)的蛋白表达及其配基的药物治疗作用。方法6-羟基多巴单侧黑质损毁法建立大鼠PD模型。免疫组织化学法观察黑质致密部mGluR1a,2/3,4,5,8和酪氨酸羟化酶(TH)的表达,并用Nissl和Fluoro-JadeB荧光双染法在激光共集焦显微镜下观察退行性变的神经元。结果6-羟基多巴导致损毁侧mGluRs和TH免疫活性下降。Ⅰ组mGluRs拮抗剂和Ⅱ,Ⅲ组mGluRs激动剂能使治疗组相应的受体表达升高,尤其是mGluR5,mGluR2/3和mGluR4的蛋白表达。其中,以APDC组(Ⅱ组mGluRs激动剂)的保护效应最为显著。5个非假手术组退行性变细胞与正常细胞的比值(D/V)均有不同程度地增高。结论mGluRs可能参与PD的发生、发展过程。Ⅰ组mGluRs拮抗剂和Ⅱ组mGluRs激动剂具有一定的神经保护功能。     

Unveiling the functions of presynaptic metabotropic glutamate receptors in the central nervous system

Metabotropic glutamate (mGlu) receptors, which include mGlu1-8 receptors, are a heterogeneous family of G-protein-coupled receptors which function to modulate brain excitability via presynaptic, postsynaptic and glial mechanisms. Certain members of this receptor family have been shown to function as presynaptic regulatory mechanisms to control release of neurotransmitters. In general, Gi-coupled mGlu receptor subtypes appear to negatively modulate excitatory (and possibly also inhibitory) neurotransmitter output when activated. Localization studies have shown that mGlu7 is restricted to the presynaptic grid at the site of vesicle fusion. These studies along with other evidence suggest that mGlu7 is the nerve terminal autoreceptor that regulates physiological release of glutamate. Other mGlu subtypes, in particular mGlu2, mGlu8, and possibly mGlu4, are also localized presynaptically, but at perisynaptic sites outside the active zone of neurotransmitter release. Gi-coupled mGlu receptors also may exist on presynaptic elements of neighboring gamma-aminobutyric acid (GABA) neurons where they play a role in heterosynaptic suppressions of GABA release. This suggests that these receptors may have evolved to monitor glutamate that has "spilled" out of the synapse. Thus, they may serve as the brain's evolutionary mechanism to prevent pathological changes in neuronal excitability and thus maintain homeostasis. Recent progress on the molecular and pharmacological aspects of these presynaptic mGlu receptors is unveiling their functions and the therapeutic directions of agents designed for these novel glutamate receptor targets.     

Antagonism of metabotropic glutamate 1 receptors attenuates behavioral effects of cocaine and methamphetamine in squirrel monkeys

Within the group I family of metabotropic glutamate receptors (mGluRs), substantial evidence points to a role for mGluR5 mechanisms in cocaine's abuse-related behavioral effects, but less is understood about the contribution of mGluR1, which also belongs to the group I mGluR family. The selective mGluR1 antagonist JNJ16259685 [(3,4-dihydro-2H-pyrano-[2,3-b]quinolin-7-yl)-(cis-4-methoxycyclohexyl)-methanone] was used to investigate the role of mGluR1 in the behavioral effects of cocaine and methamphetamine. In drug discrimination experiments, squirrel monkeys were trained to discriminate cocaine from saline by using a two-lever, food-reinforced operant procedure. JNJ16259685 (0.56 mg/kg) pretreatments significantly attenuated cocaine's discriminative stimulus effects and the cocaine-like discriminative stimulus effects of methamphetamine. In monkeys trained to self-administer cocaine or methamphetamine under a second-order schedule of intravenous drug injection, JNJ16259685 (0.56 mg/kg) significantly reduced drug-reinforced responding, resulting in a downward displacement of dose-response functions. In reinstatement studies, intravenous priming with cocaine accompanied by restoration of a cocaine-paired stimulus reinstated extinguished cocaine-seeking behavior, which was significantly attenuated by JNJ16259685 (0.56 mg/kg). Finally, in experiments involving food rather than drug self-administration, cocaine and methamphetamine increased the rate of responding, and the rate-increasing effects of both psychostimulants were significantly attenuated by JNJ16259685 (0.3 mg/kg). At the doses tested, JNJ16259685 did not significantly suppress food-reinforced behavior (drug discrimination or fixed-interval schedule of food delivery), but did significantly reduce species-typical locomotor activity in observational studies. To the extent that the psychostimulant-antagonist effects of JNJ16259685 are independent of motor function suppression, further research is warranted to investigate other mGluR1 antagonists for potential therapeutic value in psychostimulant abuse.     

Regulation of extracellular glutamate in the prefrontal cortex: focus on the cystine glutamate exchanger and group I metabotropic glutamate receptors

Microdialysis was used to determine the in vivo processes contributing to extracellular glutamate levels in the prefrontal cortex of rats. Reverse dialysis of a variety of compounds proved unable to decrease basal levels of extracellular glutamate, including Na+ and Ca2+ channel blockers, cystine/glutamate exchange (x(c)-) antagonists, and group I (mGluR1/5) and group II (mGluR2/3) metabotropic glutamate receptor (mGluR) agonists or antagonists. In contrast, extracellular glutamate was elevated by blocking Na+-dependent glutamate uptake (X(AG)-) with DL-threo-beta-benzyloxyaspartate (TBOA) and stimulating group I mGluRs with (R,S)-3,5-dihydroxy-phenylglycine (DHPG). The accumulation of extracellular glutamate produced by blocking X(AG)- was completely reversed by inhibiting system x(c)- with 4-carboxyphenylglycine (CPG), but not by Na+ and Ca2+ channel blockers. Because CPG also inhibits group I mGluRs, two additional group I antagonists were examined, LY367385 [(+)-2-methyl-4-carboxyphenylglycine] and (R,S)-1-aminoindan-1,5-dicarboxylic acid (AIDA). Whereas LY367385 also reduced TBOA-induced increases in extracellular glutamate, AIDA did not. In contrast, all three group I antagonists reversed the increase in extracellular glutamate elicited by stimulating mGluR1/5. In vitro evaluation revealed that similar to CPG, LY367385 inhibited x(c)- and that stimulating or inhibiting mGluR1/5 did not directly affect [3H]glutamate uptake via x(c)- or X(AG)-. These experiments reveal that although inhibiting x(c)- cannot reduce basal extracellular glutamate in the prefrontal cortex, the accumulation of extracellular glutamate after blockade of X(AG)- arises predominately from x(c)-. The accumulation of glutamate elicited by mGluR1/5 stimulation does not seem to result from modulating X(AG)-, x(c)-, or synaptic glutamate release.     

Central cyclooxygenase inhibitors reduced IL-1beta-induced hyperalgesia in temporomandibular joint of freely moving rats

Microinjection of formalin (5%, 50 microl) into a temporomandibular joint (TMJ) causes noxious behavioral responses in freely moving rats. In the present study, we investigated the role of central cyclooxygenase (COX) pathways in IL-1beta-induced hyperalgesia with formalin-induced TMJ pain model. Intra-articular injection of 100 pg or 1 ng of IL-1beta significantly facilitated formalin-induced behavior by 130 or 174% in the number of scratches. Intracisternal administration of 100 pg or 1 ng of IL-1beta also significantly increased formalin-induced behavior by 166 or 82% in the number of scratches. IL-1beta-induced hyperalgesia was blocked by pretreatment with IL-1 receptor antagonist. Intracisternal pretreatment with SC-560, a selective COX-1 inhibitor, or NS-398, a selective COX-2 inhibitor, abolished intra-articular administration of IL-1beta-induced hyperalgesic response. Intracisternal pretreatment with NS-398, a selective COX-2 inhibitor, abolished the intracisternal administration of IL-1beta-induced hyperalgesic response, while pretreatment with SC-560, a selective COX-1 inhibitor, did not change IL-1beta-induced hyperalgesic responses. On the other hand, pretreatment with acetaminophen, a tentative COX-3 inhibitor, also abolished both intra-articular and intracisternal administration of IL-1beta-induced hyperalgesic responses. These results indicate that central COX-2 plays important role in the central administration of IL-1beta-induced hyperalgesia and that central COX-1/2 pathways mediate peripheral administration of IL-1beta-induced hyperalgesia in the TMJ. Central COX-3 inhibitor seems to play an important role in the nociceptive process associated with both peripheral and central administration of IL-1beta-induced hyperalgesia in TMJ. It is concluded that central acting of COX-3 inhibitors may be of therapeutic value in the treatment of inflammatory pain in TMJ.     

Spinal EP receptors mediating prostaglandin E2-induced mechanical hyperalgesia, thermal hyperalgesia, and touch-evoked allodynia in rats.

Intrathecal administration of prostaglandin E(2) (PGE(2)) produces mechanical hyperalgesia, thermal hyperalgesia, and touch-evoked allodynia in rats. Experiments were conducted to examine the effects of intrathecal administration of relatively selective PGE(2) receptor (EP receptor) agonists to establish which spinal EP receptors mediate these behavioral effects of spinally administered PGE(2). Administration of either sulprostone (EP(3) receptor agonist) or PGE(1) alcohol (EP(4) receptor agonist) produced marked mechanical and thermal hyperalgesia and touch-evoked allodynia. Neither 17-phenyl trinor PGE(2) (EP(1) receptor agonist) nor butaprost (EP(2) receptor agonist) produced any significant changes in behavioral response thresholds to mechanical or thermal stimuli. However, 17-phenyl trinor PGE(2) (EP(1) receptor agonist) did produce marked touch-evoked allodynia. These data suggest that in rats activation of spinal EP(3) and EP(4) receptors by PGE(2) is important for development of both mechanical and thermal hyperalgesia as well as for touch-evoked allodynia. PGE(2)-induced allodynia also appears to involve activation of spinal EP(1) receptors.     

急性低血压对清醒大鼠前庭神经内侧核区谷氨酸和牛磺酸含量的影响

目的:利用脑部微量透析法和高效液相色谱分析法,测定静脉注射硝普钠诱发急性低血压后清醒大鼠前庭神经内侧核区细胞外液标本中谷氨酸和牛磺酸含量的变化。方法:实验于2005-02/09在延边大学基础医学院生理学教研室进行。选用Wistar系雄性大鼠,查随机数表法随机分为正常组、单侧迷路破坏损伤同侧组、单侧迷路破坏损伤对侧组,每组6只。单侧迷路破坏组左侧中耳注入对氨基苯胂酸盐损伤外周前庭器官,2周后进行实验。正常组左侧中耳注入生理盐水。腹腔注射水合氯醛麻醉,行股动静脉插管,用于血压监测和静脉给药,动、静脉插管经皮下向后背穿到头部。经股静脉注射硝普钠使动脉血压下降约30%左右。参照Paxinos&Watson大鼠脑图谱将透析膜的外套管插入到前庭神经核,透析膜的外套管内插入自制的透析导管,利用脑部微量透析法收集样本。参照Jin等方法配制诱导剂,高效液相色谱分析法观察静脉注射硝普钠诱发急性低血压后,前庭神经内侧核区细胞外液标本中谷氨酸和牛磺酸含量的变化。结果:实验纳入18只大鼠中,18只是透析探针准确进入预定区域的动物。正常组动物,静脉注射硝普钠使血压平均下降30%时,前庭神经内侧核区谷氨酸含量明显增加(P<0.01),而牛磺酸含量却明显降低(P<0.05);单侧迷路破坏损伤同侧组,诱发急性低血压后前庭神经内侧核区谷氨酸含量则无明显变化(P>0.05),牛磺酸含量明显下降(P<0.05);单侧迷路破坏损伤对侧组,诱发急性低血压后谷氨酸和牛磺酸含量都明显增加(P<0.05);诱发急性低血压后,损伤侧前庭神经内侧核区谷氨酸无显著性变化,而牛磺酸含量却明显下降,与正常组动物诱发急性低血压时前庭神经内侧核区两种氨基酸含量变化值相比谷氨酸含量变化差异显著(P<0.05),牛磺酸含量变化则不明显(P>0.05)。结论:清醒动物急性低血压影响前庭神经内侧核功能活动的过程中可能有兴奋性氨基酸-谷氨酸神经递质参与。     

Blockade of metabotropic glutamate receptor 5 activation inhibits mechanical hypersensitivity following abdominal surgery.

This study used the metabotropic glutamate 5 (mGlu5) receptor subtype-selective antagonist 2-methyl-6-(phenylethynyl)pyridine (MPEP) to characterise the contribution of mGlu5 receptor activity to pain and hypersensitivity in an animal model of post-surgical pain. Adult female Wistar rats (200–250 g) were anaesthetised with isoflurane (2%) and underwent a midline laparotomy with gentle manipulation of the viscera, and the effects of pre- (30 min) or post- (5 h) operative treatment with MPEP (1, 3 or 10 mg kg⁻¹; i.p.) or drug-vehicle on hindpaw withdrawal latency (in seconds) to thermal stimulation (Hargreave’s Test) and response threshold (in grams) to mechanical stimulation (using a dynamic plantar aesthesiometer) were measured. Animals that underwent surgery displayed significant hypersensitivity to mechanical stimulation of the hindpaws. Hypersensitivity was maximum at 6 h post-surgery (44.5 ± 2.4% decrease; p < 0.01 vs. anaesthesia only controls) and persisted for 48 h. Surgery had no effect on thermal withdrawal latency. Both pre-operative and post-operative administration of 10 mg kg⁻¹MPEP blocked mechanical hypersensitivity induced by surgery (p < 0.01 vs. vehicle treatment). MPEP had no effect on acute nociceptive thresholds in naïve animals. These data suggest that activity at mGlu5 receptors contributes to development of pain and hypersensitivity following surgery.     

Activation of metabotropic glutamate receptor 1 dimers requires glutamate binding in both subunits

Group I metabotropic glutamate receptors (mGluRs) form stable, disulfide-linked homodimers. Lack of a verifiably monomeric mGluR1 mutant has led to difficulty in assessing the role of dimerization in the molecular mechanism of mGluR1 activation. The related GABA(B) receptor exhibits striking intradimer cross talk (ligand binding at one subunit effectively produces G protein activation at the other), but it is unclear whether group I mGluRs exhibit analogous cross talk. Signaling of heterologously expressed mGluR1 was examined in isolated rat sympathetic neurons by measuring glutamate-mediated inhibition of native calcium currents. To examine mGluR1 activity when only one dimer subunit has access to glutamate ligand, wildtype mGluR1 was coexpressed with mGluR1 Y74A, a mutant with impaired glutamate binding, and the activity of the heterodimer (mutant/wild type) was examined. The mGluR1 Y74A mutant alone had a dose-response curve that was shifted by about 2 orders of magnitude. The half-maximal dose of glutamate shifted from 1.3 (wild-type mGluR1) to about 450 (mGluR1 Y74A) microM. However, the maximal effect was similar. Wild-type mGluR1 was expressed with excess Y74A mGluR1 to generate a receptor population consisting largely of mutant homodimers and mutant/wild-type heterodimers but without detectable wild-type homodimers. Under these conditions, no glutamate-mediated calcium current inhibition was observed below approximately 300 microM glutamate, although wild-type mGluR1 protein was detectable with immunofluorescence. These data suggest that mutant/wild-type heterodimeric receptors are inactive at ligand concentrations favoring glutamate association with receptor dimers at only one subunit.     

Central autonomic effects of dermorphin in conscious rats

Central cardiovascular and respiratory effects of dermorphin were studied in conscious rats. Intracerebroventricular administration (0.1 or 1 nM) of dermorphin increased the systolic and diastolic blood pressure whereas a high dose (50 nM) decreased blood pressure. Dermorphin at 1 nM increased respiratory rate but caused hypoxia, acidosis and hypercapnia; at 50 nM, respiratory rate was suppressed. Both of these doses produced catalepsy. Stimulation of the sympathoadrenomedullary axis at the pressor period elicited by 1 nM dermorphin was evident by high circulating levels of epinephrine and norepinephrine. N-methyl-atropine reversed the severe bradycardia induced by dermorphin and completely prevented this phenomenon if given as pretreatment. Neither blood pressure nor respiratory depression was altered by the muscarinic blocker. Naloxone (1 mg/kg) reversed the respiratory, cardiovascular and sympathetic effects of dermorphin as well as the catalepsy. These data show that dermorphin has central autonomic effects which are naloxone reversible and mediated by both sympathetic and parasympathetic pathways.     

急性低血压对清醒大鼠前庭神经内侧核区谷氨酸和牛磺酸含量的影响

目的：利用脑部微量透析法和高效液相色谱分析法，测定静脉注射硝普钠诱发急性低血压后清醒大鼠前庭神经内侧核区细胞外液标本中谷氨酸和牛磺酸含量的变化。 方法：实验于2005-02／09在延边大学基础医学院生理学教研室进行。选用Wistar系雄性大鼠，查随机数表法随机分为正常组、单侧迷路破坏损伤同侧组、单侧迷路破坏损伤对侧组，每组6只。单侧迷路破坏组左侧中耳注入对氨基苯胂酸盐损伤外周前庭器官，2周后进行实验。正常组左侧中耳注入生理盐水。腹腔注射水合氯醛麻醉，行股动静脉插管，用于血压监测和静脉给药，动、静脉插管经皮下向后背穿到头部。经股静脉注射硝普钠使动脉血压下降约30％左右。参照Paxinos＆Watson大鼠脑图谱将透析膜的外套管插入到前庭神经核，透析膜的外套管内插八自制的透析导管，利用脑部微量透析法收集样本。参照Jin等方法配制诱导剂，高效液相色谱分析法观察静脉注射硝普钠诱发急性低血压后，前庭神经内侧核区细胞外液标本中谷氨酸和牛磺酸含量的变化。 结果：实验纳入18只大鼠中，18只是透析探针准确进入预定区域的动物。正常组动物，静脉注射硝普钠使血压平均下降30％时，前庭神经内侧核区谷氨酸含量明显增加（P〈0．01），而牛磺酸含量却明显降低（P〈0．05）；单侧迷路破坏损伤同侧组，诱发急性低血压后前庭神经内侧核区谷氨酸含量则无明显变化（P〉0．05），牛磺酸含量明显下降（P〈0．05）；单俱十迷路破坏损伤对侧组，诱发急性低血压后谷氨酸和牛磺酸含量都明显增加（P〈0．05）；诱发急性低血压后，损伤侧前庭神经内侧核区谷氨酸无显著性变化，而牛磺酸含量却明显下降，与正常组动物诱发急性低血压时前庭神经内侧核区两种氨基酸含量变化值相比谷氨酸含量变化差异显著（P〈0．05），牛磺酸含量变化则不明显（P〉0．05）。 结论：清醒动物急性低血压影响前庭神经内侧核功能活动的过程中可能有兴奋性氨基酸一谷氨酸神经递质参与。     

3H]LY341495 binding to group II metabotropic glutamate receptors in rat brain.

[3H]LY341495 is a highly potent and selective antagonist for group II metabotropic glutamate (mGlu) receptors (mGlu2 and mGlu3), which has been used to label these receptors in cells expressing recombinant receptor subtypes. In this study, we characterized the kinetics, pharmacology, and distribution of [3H]LY341495 binding to mGlu receptors in rat brain tissue. Equilibrium experiments in the rat forebrain demonstrated binding to a single site that was saturable, reversible, and of high affinity (Bmax, 3.9 +/- 0.65 pmol/mg of protein, Kd, 0.84 +/- 0.11 nM). The relative order of potencies for displacement of [3H]LY341495 by mGlu receptor ligands was LY341495 > L-glutamic acid > LY354740 > (2S,1'S,2'S)-2-(carboxycyclopropyl)glycine > 4-(2R,4R)-aminopyrrolidine-2,4-dicarboxylate > (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid > (R,S)-alpha-methyl-4-phosphonophenylglycine > (R,S)3,5-dihydroxyphenylglycine > L-(+)-2-amino-4-phosphonobutyric acid. [3H]LY341495 was not displaced by the selective ionotropic glutamate receptor agonists N-methyl-D-aspartic acid, (R,S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, or kainate at concentrations up to 1 mM. Comparison of [3H]LY341495 binding in rat brain with recombinant mGlu receptor subtypes demonstrated a very high correlation with mGlu3 receptor binding (r2 = 0.957), a significant, but lower, correlation with mGlu2 receptor binding (r2 = 0.869), but no significant correlation to mGlu8 receptor binding (r2 = 0.284). Regional studies using autoradiography showed a similar distribution of [3H]LY341495 binding to that for group II mGlu receptors previously reported by others using immunocytochemical techniques. These studies indicate that [3H]LY341495 selectively labels group II (mGlu2/3) receptors, but under the conditions used, [3H]LY341495 may bind predominately to mGlu3 receptor populations in the rat forebrain.     

Nitric oxide synthase inhibitors inhibit interleukin-1 beta-induced depression of vascular smooth muscle.

Interleukin-1 beta (IL-1) reduces vascular smooth muscle contractility. The purpose of the present study was to investigate the role of nitric oxide synthesis in mediating this effect of IL-1. We studied the influence of inhibitors of nitric oxide synthesis on the depression of norepinephrine-induced contractions of rat aortic rings by IL-1. Also, we examined the ability of IL-1 to increase the production of nitric oxide by rat aortic smooth muscle cells in culture as determined indirectly by measuring nitrite concentrations. NG-amino-L-arginine blocked the effect of IL-1 on norepinephrine-induced contractions of rat aortic rings whereas NG-monomethyl-L-arginine and NG-nitro-L-arginine were considerably less effective. In addition, this effect of IL-1 was prevented by coincubation of the rings with cycloheximide. IL-1 greatly elevated nitrite production by rat aortic smooth muscle cells, and this effect could also be blocked completely by the arginine analogs. NG-amino-L-arginine was the most potent inhibitor of nitrite synthesis (IC50 = 1.7 microM) whereas NG-monomethyl-L-arginine and NG-nitro-L-arginine were about 10-fold less potent (IC50 = 16 and 22 microM, respectively). These results suggest that IL-1-induced depression of norepinephrine-induced vascular contraction is mediated by the increased synthesis of nitric oxide synthase by vascular smooth muscle cells. The relative potency of the arginine analogs for the inhibition of nitrite synthesis suggests that the synthase in vascular smooth muscle is similar to the synthase in macrophages.     

Adrenergic sensitivity of the sensory receptors modulating mechanical allodynia in a rat neuropathic pain model

This study focuses on changes in adrenergic sensitivity in untransected sensory axons that innervate an area of skin made neuropathic by transection of neighboring nerves. The segmental nerve injury model is favorable for this since all axons in the L5 and L6 nerves are transected whereas the L4 axons are intact. Earlier findings are that pain behaviors develop after this injury and that these beahviors are ameliorated by sympathectomy. The present study shows that behavior indicating mechanical allodynia can be rekindled after sympathectomy by intradermal norepinephrine and -2 but not -1 adrenergic ligands and the rekindling can be blocked by -2 but not -1 adrenergic antagonists. By contrast neither intradermal norepinephrine nor other adrenergic agonists or antagonists have any demonstrable effects in the normal or after either neuropathic surgery or sympathectomy alone. These data suggest that the combination of neuropathic surgery and sympathectomy results in an upregulation of active -2 adrenergic receptors on the undamaged sensory axons that provide the remaining sensory innervation to a neuropathic area partially denervated by segmental nerve lesions. These changes on undamaged axons presumably compliment similar changes on the transected axons and, thus play a role in the development of neuropathic pain.