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Biomedical subjects

Qiang Chen

Publications and source records attributed to Qiang Chen.

At least 37 records · Page 2Linked to original sources

[Observation on therapeutic effect of "reducing south and reinforcing north" needling method on hypertension of type of yang-hyperactivity due to yin-deficiency].

OBJECTIVE: To observe therapeutic effect of "reducing south and reinforcing north" needling method on hypertension of type of yang-hyperactivity due to yin-deficiency, METHODS: Ninety cases of hypertension were randomly divided into a treatment group (n=59) treated with "reducing south and reinforcing north" needling method, and a control group (n=31) treated with capoten and aspirin. Their therapeutic effects on symptoms and blood pressure were compared. RESULTS: The total effective rate was 93.2% in the treatment group and 77.4% in the control group, the treatment group being better than the control group (P<0.05). After treatment, systolic pressure and diastolic pressure in the two groups decreased (P<0.05), but with no significant difference between the two groups in the therapeutic effect of reducing blood pressure (P>0.05). CONCLUSION: "Reducing south and reinforcing north" needling method and oral administration of capoten and aspirin have similar effect in reducing blood pressure, and the treatment group is better than the control group in improving symptoms.

Blood Pressure↗

[Study on the association between estrogen receptor alpha gene polymorphism and intrahepatic cholestasis of pregnancy].

OBJECTIVE: To investigate the relationship between estrogen receptor alpha (ERalpha) gene polymorphism and intrahepatic cholestasis of pregnancy (ICP). METHODS: The Xba I and Pvu II polymorphisms in intron 1 of ER alpha gene were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method in 100 pregnant women with ICP (ICP group) and 100 normal pregnant women (control group). RESULTS: (1) The frequencies of XX, Xx and xx genotypes of Xba I polymorphism were 6%, 33% and 61% respectively in control group, and were 2%, 33% and 65% respectively in ICP group. There was no significant difference in the distribution of Xba I genotypes between the two groups (P > 0.05). The frequencies of the two alleles X and x were 23% and 78% in control group, and were 19% and 82% in ICP group, respectively. There was also no significant difference in the frequency of Xba I alleles between the two groups (P > 0.05). (2) The frequencies of PP, Pp and pp genotypes of Pvu II polymorphism were 18%, 42% and 40% respectively in control group, and were 12%, 53% and 35% respectively in ICP group. There was no significant difference in the distribution of Pvu II genotypes between the two groups (P > 0.05). The frequencies of the two alleles P and p were 39% and 61% in control group, and were 39% and 62% in ICP group, respectively. There was also no significant difference in the frequency of Pvu II alleles between the two groups (P > 0.05). (3) There was also no significant difference in the distribution of Xba I and Pvu II combinative genotype between the two groups (P > 0.05). CONCLUSION: The ERalpha gene polymorphism is not associated with the risk of ICP.

Adult↗

[Effects of yiqi huoxue method on cardiac function in patients with congestive heart failure].

OBJECTIVE: To compare the clinical effect of three TCM therapeutic methods, Yiqi (YQ, supplementing Qi), Huoxue (HX, activating blood circulation) and Yiqi Huoxue (YQHX) method on congestive heart failure and heart function. METHODS: Eighty patients were divided into 3 groups randomly, they were treated by conventional therapy and with the additional TCM drugs for YQHX to group A (n = 36), drugs for YQ to group B (n = 24), and drugs for HX to group C (n = 20). After 2 weeks' treatment, clinical effect was observed and cardiac function was detected and compared. RESULTS: The total effective rate was 91.7% in group A, which was superior to that in group B (66.7%) and group C (65.0%) respectively. Cardiac function was improved remarkably after treatment in all groups, the optimal effect was shown in group A. CONCLUSION: All the 3 methods could improve clinical symptoms and cardiac function in patients with congestive heart failure, among which YQHX method has the optimal effect.

Aged↗

[Off-line experiments and analysis of independent brain--computer interface].

In order to study event-related desynchronization (ERD) related to voluntary movement, we designed two experiments. In the first experiment, untrained subjects were required to imagine the action of typing with left or right index finger for about 1 second before real action, whereas they were required to type instantly after instruction in the second experiment. By analyzing spontaneous EEG signals between the instruction and the action, we predicted which finger was used. The prediction accuracy in the first experiment fell from 85% to 71% with the progress of experiment, the average accuracy being 78%, whereas the prediction result was almost random guess in the second experiment. The results demonstrate that (1) ERD patterns are significantly affected by the effective duration of motion imagination, (2) unconscious reduction of this duration can decrease the prediction accuracy. Therefore, when designing subsequent BCI experiments, we should devote our attention to the question of how to keep the effective duration of motion imagination.

Brain↗

[Phase I/II clinical trial of weekly administration of docetaxel plus cisplatin for advanced non-small cell lung cancer].

OBJECTIVE: The purpose of this phase I/II study is to investigate the safety/toxicity profile of weekly administration of docetaxel in combination with cisplatin for the chemo-naive patients with advanced non-small cell lung cancer (NSCLC), and to evaluate the efficacy of this regime. METHODS: In phase I trial, 15 patients were included. IV infusion of escalating doses of docetaxel consisting of four levels from 25 to 40 mg/m2 (25, 30, 35, 40 mg/m2) on D1, 8, 15 and cisplatin of 75 mg/m2 on D1 was administered. The regime was repeated every 4 weeks. Blood samples were obtained on D1, 15 in the first cycle to measure the PK. Dose limiting toxicity (DLT) was determined in cycle 1 and defined as any grade 3 non-hematologic toxicity which could not be reverted into grade less than grade 2 within 4 days or any grade 4 hematologic toxicity. Eighty-three patients completed their phase II study with administration of docetaxel at a dose of 35 mg/m2 based on the data of phase I trial. RESULTS: In the phase I trial, grade 3/4 neutropenia was mainly observed in patients who received docetaxel of 40 mg/m2 (level 4) with one patient suffering from an infection signifying dose limiting toxicity (DLT). Non-hematological toxicities including nausea/vomiting, alopecia, fluid retension and asthenia were tolerable. Based on these data, the maximum tolerence dose (MTD) did not reach the level of weekly giving docetaxel at a dose of 40 mg/m2 in combination with cisplatin 75 mg/m2 every 4 weeks. The pharmacokinetic/dynamics results There was no statistically significant difference between clearance value among the 4 dose levels of docetaxel from 25 to 40 mg/m2 when measured by Cmax and AUC. The pharmacokinetics of docetaxel was not influenced by the presence of co-administration of cisplatin when compared D1 with D15 as based on CmaxN, AUCN and CL. In the phase II trial, totally 83 patients received 216 cycles of chemotherapy. One CR (complete response) and 22 PR (partial response) were achieved with an objective response rate of 27.7% in this series and 30.7% in the evaluable patients. The 1-year survival was 48.6% with a median survival of 10.7 months (range: 3-34 months). Hematologic toxicities were the major side effects, though most were mild; grade III/IV neutropenia developed in 15%. The common non-hematologic toxicities were nausea, vomiting and asthenia. CONCLUSION: Weekly consecutive administration of docetaxel on D1, 8, 15 for 3 weeks plus cisplatin on D1 is tolerable and effective with minimal myelosuppression in chemo-naive patients with advanced NSCLC.

Adult↗

[An associated analysis of estrogen receptor 2 gene polymorphism linked with intrahepatic cholestasis of pregnancy].

OBJECTIVE: To investigate the relation ship of estrogen receptor 2 gene (ESR2) polymorphism associated with intrahepatic cholestasis of pregnancy (ICP) in Chengdu of China. METHODS: By polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method, the Rsa I polymorphism in exon 5 and the Alu I polymorphism in exon 8 of ESR2 were detected in 100 pregnant women with ICP (ICP group) and 100 normal pregnant women (control group) in Chengdu. RESULTS: (1) The frequency of the allele A of Alu I polymorphism in exon 8 was significantly higher in ICP group than in control group (P=0.031, OR=1.975), so did the frequency of the Aa+AA genotypes (P=0.028, OR=2.144). (2) The genotype distributions (rr, Rr and RR) and allele frequencies (r and R) of Rsa I polymorphism in exon 5 were not significantly different between the two groups (P>0.05). CONCLUSION: The Alu I polymorphism in exon 8 of ESR2 may be associated with the susceptibility of ICP in Chengdu. The Aa+AA genotype significantly elevated the risk suffering from the ICP. The Rsa I polymorphism in exon 5 of ESR2 is not associated with the risk getting the ICP in Chengdu.

Cholestasis, Intrahepatic↗

[Effects of abscisic acid on photosynthetic characteristics and antioxidant enzyme activities of wheat seedlings].

This paper studied the effects of short- and long term abscisic acid (ABA) treatments on the CO2 assimilation (Pn), carboxylation efficiency (CE), response of Pn to CO2, and antioxidant enzyme activities of wheat seedlings exposed to UV-C. The results showed that under no UV-C, short- and long term ABA treatments increased Pn by 14.69% and 20.46%, and decreased stomatal conductance (Gs) by 14.74% and 17.31%, respectively, compared to the control, while no effects were observed on intercellular CO2 concentration (Ci) and CE. Under UV-C, the Pn, CE, Gs and Ci decreased, with the least decrease in long term ABA treatment, less in short term ABA treatment, and the most in control. ABA could increase the response of Pn to CO2, while UV-C inhibited it. In ABA treatments, antioxidant enzyme activities were enhanced, while MDA content was decreased. Under UV-C, CAT activity increased first, reached its maximum after 1 h, and decreased then. The activities of SOD and POD in ABA treatments increased first and decreased then, with the greater increase in long term ABA treatment than in short term ABA treatment, while those in the control decreased. It was suggested that through enhancing Pn and antioxidant enzyme activities, ABA could enhance the resistance of wheat to UV-C, and long term ABA treatment had better effects than short term ABA treatment.

Abscisic Acid↗

[Association between polymorphisms of CYP17 and CYP3A4 genes and intrahepatic cholestasis of pregnancy in Chengdu].

OBJECTIVE: investigate whether polymorphisms in estrogen-metabolizing genes, CYP17 and CYP3A4, are associated with intrahepatic cholestasis of pregnancy (ICP) in Chengdu China. METHODS: The -1931T/C polymorphism in the 5'-untranslated region of CYP17 gene and the -290A/G polymorphism in the 5'-regulatory region of CYP3A4 gene were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method in 100 pregnant women with ICP (ICP group) and 100 normal pregnant women (control group) in Chengdu. RESULTS: The T/C polymorphism of the CYP17 gene was shown clearly in ICP and control groups, but the genotype distributions (TT, TC and CC) and allele frequencies (T and C) of CYP17 polymorphism were of no significant difference between the two groups (P > 0.05). No CYP3A4-V (CTP3A4 * 1B) allele was found in the 200 individuals studied. The genotype of CYP3A4 was wt/wt in all the pregnant women. CONCLUSION: The T/C polymorphism of CYP17 gene is not associated with the risk of ICP in Chengdu. There are not -290A/G polymorphism of CYP3A4 gene among pregnunt women in Chengdu.

China↗

[Association of genetic polymorphisms in human leukocyte antigen-DQA1 with intrahepatic cholestasis of pregnancy in Chengdu district].

OBJECTIVE: To explore the relationship between human leukocyte antigen-DQA1 (HLA-DQA1) allele gene polymorphism and intrahepatic cholestasis of pregnancy (ICP). METHODS: Forty-five patients with ICP, eighteen ICP families, forty-five normal pregnant women and eighteen normal control families were tested for HLA-DQA1 allele gene polymorphism by polymerase chain reaction with sequence-specific primer (PCR-SSP) method. RESULTS: The frequency of HLA-DQA1*0301 in normal pregnant women was markedly higher than that in the ICP group (P>0.05). No significant differences were observed between the frequencies of other detected HLA-DQA1 alleles in both groups. The analysis of feto-maternal or couples sharing of the HLA-DQA1 alleles showed that no significant differences were observed between the two groups. CONCLUSION: The above findings suggest that there is no significant association between the genetic polymorphisms in HLA-DQA1 and ICP in Chengdu district; HLA-DQA1*0301 may be a protective gene against ICP. It may prevent the development of ICP.

Adult↗

[Human amnion cells express the phenotypes of neural cells and adipocytes in vitro].

OBJECTIVE: To search for culture conditions in which the cells from human amnion could diferentiate into neural cells and hence to explore a new cell source for neural transplantaion. METHODS: Amnion cells from human were cultured with tissue piece method, passaged by trypsin digestion and identified with immunocytochemistry. RESULTS: Amnion cells migrated from explants and primary culture was established; they could multiply and expand steadily in a short time, and they could be passaged by trypsin digestion. When cultured in serum-free neural stem cell media, these cells could form the same spheroid shape as the neurospheres of neural stem cells. They could express alpha smooth muscle actin and differentiate into smooth muscle cells spontaneously, and could express nestin and vimentin, the markers for neural progenitors. Moreover, they could he stained by anti-beta III-tubulin, anti-neurofilament 200 and anti-NSE; the majorities could he stained by antityrosine hydroxylase, the marker for dopaminergic neurons. Lower than 0.1% of the total cells were stained by GFAP, indicating the existence of astrocytes. The amnion cells could also differentiate into adipocytes under specific induction. CONCLUSION: Amnion cells could differentiate into adipocytes and smooth muscle cells; they could express the protein for neural cells; thus may represent an alternative stem cell source for CNS cell transplantation.

Adipocytes↗

PI3 kinase is involved in cocaine behavioral sensitization and its reversal with brain area specificity.

Phosphatidylinositol 3-kinase (PI3K) is an important signaling molecule involved in cell differentiation, proliferation, survival, and phagocytosis, and may participate in various brain functions. To determine whether it is also involved in cocaine sensitization, we measured the p85alpha/p110 PI3K activity in the nuclear accumbens (NAc) shell, NAc core, and prefrontal cortex (PFC) following establishment of cocaine sensitization and its subsequent reversal. Naïve rats were rank-ordered and split into either daily cocaine or saline pretreatment group based on their locomotor responses to an acute cocaine injection (7.5 mg/kg, i.p.). These two groups were then injected with cocaine (40 mg/kg, s.c.) or saline for 4 consecutive days followed by 9-day withdrawal. Cocaine sensitization was subsequently reversed by 5 daily injections of the D1/D2 agonist pergolide (0.1 mg/kg, s.c.) in combination with the 5-HT3 antagonist ondansetron (0.2 mg/kg, s.c., 3.5h after pergolide injection). After another 9-day withdrawal, behavioral cocaine sensitization and its reversal were confirmed with an acute cocaine challenge (7.5 mg/kg, i.p.), and animals were sacrificed the next day for measurement of p85alpha/p110 PI3K activity. Cocaine-sensitized animals exhibited increased PI3K activity in the NAc shell, and this increase was reversed by combined pergolide/ondansetron treatment, which also reversed behavioral sensitization. In the NAc core and PFC, cocaine sensitization decreased and increased the PI3K activity, respectively. These changes, in contrast to that in the NAc shell, were not normalized following the reversal of cocaine-sensitization. Interestingly, daily injections of pergolide alone in saline-pretreated animals induced PI3K changes that were similar to the cocaine sensitization-associated changes in the NAc core and PFC but not the NAc shell; furthermore, these changes in saline-pretreated animals were prevented by ondansetron given 3.5h after pergolide. The present study suggests that selective enhancement of the PI3K activity in the NAc shell may be one of key alterations underlying the long-term cocaine sensitization. To the extent cocaine sensitization is an important factor in human cocaine abuse, pharmacological interventions targeted toward the NAc shell PI3K alteration may be useful in cocaine abuse treatment.

Animals↗

In vitro and in vivo studies of dansylated compounds, the putative agonists and antagonists on neuropeptide FF receptors.

To further evaluate the importance of C-terminal modification of neuropeptide FF (NPFF), in the present work, four dansylated NPFF analogues, including two putative agonists (dansyl-PQRFamide and dansyl-GSRFamide) and two putative antagonists (dansyl-PQRamide and dansyl-GSRamide), were synthesized and investigated to address their potencies and efficacies in a series of in vitro and in vivo assays. (1) In the isolated mouse colon bioassay, the four dansylated compounds showed agonistic profiles: both dansyl-GSRFamide (1-10 microM) and dansyl-GSRamide (1-10 microM) dose-dependently caused colonic contractions, which were attenuated by pretreatment with BIBP3226; dansyl-PQRFamide and dansyl-PQRamide evoked modest colonic contractions at a high dose of 50 microM. (2) In urethane-anaesthetized rats, both dansyl-PQRFamide (50-300 nmol/kg, i.v.) and dansyl-GSRFamide (15-50 nmol/kg, i.v.) dose-dependently increased the mean arterial pressure and heart rate in a manner similar to NPFF (50-300 nmol/kg, i.v.); on the contrary, the two putative antagonists (100-800 nmol/kg, i.v.) decreased blood pressure in a dose-dependent manner. All the results suggest that dansyl-PQRFamide and dansyl-GSRFamide are NPFF full agonists; in contrast, dansyl-GSRamide and dansyl-PQRamide behave as agonists in vitro and antagonists in vivo on NPFF receptors. The findings reveal that the C-terminal Phe might be a crucial residue to determine the efficacy. In addition, the novel analogue dansyl-GSRFamide may be developed as a highly potent agonist to investigate the NPFF system.

Animals↗

Oxytocin modulates neural circuitry for social cognition and fear in humans.

In non-human mammals, the neuropeptide oxytocin is a key mediator of complex emotional and social behaviors, including attachment, social recognition, and aggression. Oxytocin reduces anxiety and impacts on fear conditioning and extinction. Recently, oxytocin administration in humans was shown to increase trust, suggesting involvement of the amygdala, a central component of the neurocircuitry of fear and social cognition that has been linked to trust and highly expresses oxytocin receptors in many mammals. However, no human data on the effects of this peptide on brain function were available. Here, we show that human amygdala function is strongly modulated by oxytocin. We used functional magnetic resonance imaging to image amygdala activation by fear-inducing visual stimuli in 15 healthy males after double-blind crossover intranasal application of placebo or oxytocin. Compared with placebo, oxytocin potently reduced activation of the amygdala and reduced coupling of the amygdala to brainstem regions implicated in autonomic and behavioral manifestations of fear. Our results indicate a neural mechanism for the effects of oxytocin in social cognition in the human brain and provide a methodology and rationale for exploring therapeutic strategies in disorders in which abnormal amygdala function has been implicated, such as social phobia or autism.

Adolescent↗

Structure-activity studies on different modifications of nociceptin/orphanin FQ: identification of highly potent agonists and antagonists of its receptor.

Nociceptin/orphanin FQ (N/OFQ) and its receptor system modulate a variety of biological functions and further understandings of physiological and pathological roles of this system require new potent agonists and antagonists of its receptor. Two series of N/OFQ related analogues were synthesized to investigate the relationship of different modifications. We combined modifications including: (a) Phe(4)-->(pF)Phe(4); (b) Ala(7), Ala(11)-->Aib(7), Aib(11); (c) Leu(14), Ala(15)-->Arg(14), Lys(15). Compared with the first series, N-terminus of the second series was changed from Phe(1) to Nphe(1). All the analogues were amidated at C-terminus. These compounds were tested in binding studies on rat brain membranes and mouse vas deferens assay. Results indicated that the compounds of the first series showed higher affinity and potency than N/OFQ (pK(i)=9.33; pEC(50)=7.50). In particular, [(pF)Phe(4), Aib(7), Aib(11), Arg(14), Lys(15)] N/OFQ-NH(2) was found to be a highly potent agonist with pK(i)=10.78 in binding studies and pEC(50)=9.37 in mouse vas deferens assay. The second series all competitively antagonized the effects of N/OFQ in mouse vas deferens assay. [Nphe(1), (pF)Phe(4), Aib(7), Aib(11), Arg(14), Lys(15)] N/OFQ-NH(2) was the best antagonist with pA(2)=8.39 and showed high binding affinity with pK(i)=9.99. Thus modifications which increase the potency of agonist have synergistic effect on biological activity and a replacement of N-terminus leads to shift of analogues from agonist to antagonist.

Animals↗

Effects and mechanisms of supraspinal administration of rat/mouse hemokinin-1, a mammalian tachykinin peptide, on nociception in mice.

Rat/mouse hemokinin 1 (r/m HK-1) is a novel tachykinin peptide whose biological functions are not fully understood. This work was designed to observe the effects of r/m HK-1 in pain modulation at supraspinal level in mice using tail-flick test. Intracerebroventricular (i.c.v.) administration of r/m HK-1 (0.1, 0.3, 1, 3 nmol/mouse) dose-dependently induced potent analgesic effect (ED(50) = 0.2877 nmol/mouse). When r/m HK-1 co-injected (i.c.v.) with SR140333 (a selective NK(1) receptor antagonist), SR140333 could fully antagonize the analgesic effect of r/m HK-1. The maximal analgesic effect of r/m HK-1 (3 nmol/mouse) could also be reversed by naloxone (i.p., 2 mg/kg). However, i.c.v. low dose administration of r/m HK-1 (10, 3, 1 pmol/mouse) induced hyperalgesia with a "U" shape curve, which means that the maximal hyperalgesic effect appeared at 3 pmol/mouse, and this effect of r/m HK-1 could also be fully blocked by SR140333. Interestingly, [Nphe(1)]NC(1-13)NH(2), a selective opioid receptor like-1 (ORL-1) receptor antagonist, could fully reverse the maximal hyperalgesic effect of r/m HK-1 (3 pmol/mouse). In addition, when r/m HK-1 co-injected (i.c.v.) with SR48968 (a selective NK(2) receptor antagonist), SR48968 could hardly affect the nociceptive effects of r/m HK-1 either at nanomole concentration or at picomole concentration. These findings suggested that r/m HK-1 might play an important role in pain modulation at supraspinal level in mice and these effects were first elicited through the activation of NK(1) receptor, subsequently, whether activation of the classical opioid receptor or the ORL1 receptor depending on the dose of i.c.v. administration of r/m HK-1.

Analysis of Variance↗

Soluble expression, purification, and stabilization of a pro-apoptotic human protein, CARP.

CARP is a novel pro-apoptotic protein that has been cloned and characterized in our previous report. Previous studies showed that suppression of CARP expression results in cell proliferation in several mammalian cell lines and over-expression of CARP leads to apoptosis and inhibition of proliferation in seven tumor cell lines [Liu et al., CARP is a novel caspase recruitment domain containing pro-apoptotic protein, Biochem. Biophys. Res. Commun. 293 (2002) 1396]. To obtain soluble and active form of CARP protein for further functional and structural studies, we have expressed CARP in Escherichia coli by using Gateway cloning system. Optimal induction and expression conditions were also studied. Recombinant histidine-tagged CARP was expressed in E. coli when the carp gene was subcloned into a Gateway expression vector pET21-DEST. The partially soluble recombinant CARP protein was purified to near homogeneity by a two-step FPLC procedure, first by Ni2+ affinity chromatography followed by a gel-filtration chromatography, which yielded about 10 mg protein/L culture with at least 95% purity. Two peaks were detected in the analytical gel-filtration chromatograph while only one peak corresponding to monomer of the CARP protein was left after adding 2 mM dithiothreitol (DTT). The polymers observed are likely due to the formation of intermolecular disulfide bridges. These results suggest that adding DTT is a good solution to prevent the formation of disulfide bonds and to stabilize the protein. Successfully growing crystals of the purified CARP protein also proved that we can produce well folded CARP protein in E. coli.

Apoptosis↗

Endomorphin 1[psi] and endomorphin 2[psi], endomorphins analogues containing a reduced (CH2NH) amide bond between Tyr1 and Pro2, display partial agonist potency but significant antinociception.

Endomorphin 1 (EM1) and endomorphin 2 (EM2) are highly potent and selective mu-opioid receptor agonists and have significant antinociceptive action. In the mu-selective pocket of endomorphins (EMs), Pro2 residue is a spacer and directs the Tyr1 and Trp3/Phe3 side chains into the required orientation. The present work was designed to substitute the peptide bond between Tyr1 and Pro2 of EMs with a reduced (CH2NH) bond and study the agonist potency and antinociception of EM1[psi] (Tyr[psi(CH2NH)]Pro-Trp-Phe-NH2) and EM2[psi] (Tyr[psi(CH2NH)]Pro-Phe-Phe-NH2). Both EM1[psi] and EM2[psi] are partial mu opioid receptor agonists showing significant loss of agonist potency in GPI assay. However, EMs[psi] exhibited potent supraspinal antinociceptive action in vivo. In the mice tail-flick test, EMs[psi] (1, 5, 10 nmol/mouse, i.c.v.) produced potent and short-lasting antinociception in a dose-dependent and naloxone (1 mg/kg) reversed manner. At the highest dose of 10 nmol, the effect of EM2[psi] was prolonged and more significant than that of EM2. In the rat model of formalin injection induced inflammatory pain, EMs[psi] (0.1, 1, 10 nmol/rat, i.c.v.), like EMs, exerted transient but not dose-dependent antinociception. These results suggested that in the mu-selective pocket of EMs, the rigid conformation induced by the peptide bond between Tyr1 and Pro2 is essential to regulate their agonist properties at the mu opioid receptors. However, the increased conformational flexibility induced by the reduced (CH2NH) bond made less influence on their antinociception.

Amides↗