Search

Objectives: Intracerebroventricular injection of endothelin-A receptor antagonist BQ123 potentiates opioid analgesia and reverses analgesic tolerance. This study explores whether these effects can be replicated by injecting BQ123 intravenously., Methods: Male Swiss-Webster mice were used. Morphine tolerance was induced using 3- or 7-day dosing. Intravenous BQ123 (8 mg/kg) was injected only once on Day 1, 2, 3 or 4 (3-day studies), and on Day 4, 6 or 8 (7-day studies). On Day 4 or 8, respectively, tail-flick and hot-plate latencies were measured following a morphine challenge dose., Key Findings: Intravenous BQ123 increased the potency and duration of morphine antinociceptive responses. In the 3-day study, the antinociceptive response was unaffected by BQ123 given on Days 1 or 2. BQ123 treatment on Day 3 or 4 (Day 4, BQ123 given 15-min before morphine) significantly potentiated antinociceptive response versus vehicle-treated tolerant mice. In 7-day studies, the antinociceptive response was unaffected by BQ123 given on Day 4. BQ123 given on Day 6 or 8 (Day 8, BQ123 given 15-min before morphine) produced a >100% increase in antinociceptive response versus vehicle-treated tolerant mice for at least 48 h., Conclusions: Intravenous administration of BQ123 is effective in potentiating morphine analgesia and restoring antinociceptive response in morphine-tolerant mice., (© The Author(s) 2022. Published by Oxford University Press on behalf of the Royal Pharmaceutical Society. All rights reserved. 
For permissions, please e-mail: journals.permissions@oup.com.)

During the COVID-19 pandemic lasting now for well more than a year, nearly 247 million cases have been diagnosed and over 5 million deaths have been recorded worldwide as of November 2021. The devastating effects of the SARS-CoV-2 virus on the immune system lead to the activation of signaling pathways involved in inflammation and the production of inflammatory cytokines. SARS-CoV-2 displays a great deal of homology with other coronaviruses, especially SARS-CoV and MERS-CoV which all display similar components which may serve as targets, namely the Spike (S) protein, the main protease (M Pro ) which is a chymotrypsin-like protease (CL Pro ) and RNA-directed RNA polymerase (RdRp). Natural constituents found in traditional herbal medicines, dietary supplements and foods demonstrate activity against SARS-CoV-2 by affecting the production of cytokines, modulating cell signaling pathways related to inflammation and even by direct interaction with targets found in the virus. This has been demonstrated by the application of fluorescence resonance energy transfer (FRET) experiments, assays of cytopathic effect (CPE) and in silico molecular docking studies that estimate binding strength. Glycyrrhizin, flavonoids such as quercetin, kaempferol and baicalein, and other polyphenols are the most common constituents found in Traditional Chinese Medicines that modulate inflammation and cell signaling pathways, and bind viral targets demonstrating valuable effects against SARS-CoV-2. However, the bioavailability of these natural products and their dependence on each other in extracts make it difficult to assess their actual utility in the treatment of COVID-19. Therefore, more can be learned through rational drug design based on natural products and from well-designed clinical trials employing specific doses of standardized combinations., Competing Interests: Conflict of interestThe authors declare no competing interests., (© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2021.)

Centhaquin has been shown to produce antinociception in the mouse hot plate and tail flick assays through the opioid, the α2A and α2B adrenoceptors. Present study was conducted to determine the effects of centhaquin in a rat model of postoperative pain. Involvement of opioid, and adrenergic receptors was assessed by pretreating rats with antagonists at the opioid (naloxone), α2-(atipamezole) or α2B-(imiloxan) adrenergic receptors. Postoperative pain was induced by hind paw plantar incision in male Sprague Dawley rats. Antihyperalgesic effects were determined by measurement of paw withdrawal latencies and withdrawal force, using dynamic von Frey filaments; attenuation of non-evoked guarding was measured by assigning pain scores to spontaneous behaviors. Rotarod test was used to determine motor impairment. Animals received saline, centhaquin or antagonist plus centhaquin. Centhaquin produced dose-dependent antihyperalgesic effect and attenuation of non-evoked guarding behavior, versus saline treated rats (P<0.05). Naloxone partially blocked while atipamezole and imiloxan significantly reversed centhaquin's antihyperalgesic effects (P<0.05). Attenuation of non-evoked guarding behavior was also blocked, but was not statistically significant. Imiloxan produced a greater block compared to atipamezole while naloxone had no significant effect. Rotarod testing indicated that centhaquin did not cause motor impairment. This is the first report demonstrating centhaquin antinociception in the rat postoperative pain model. Opioid, α2 adrenergic, and particularly α2B adrenergic receptors are involved in mediating antihyperalgesia while attenuation of nonevoked guarding is mediated by α2B/α2 adrenergic receptors. Centhaquin could be an effective non-sedating alternative in treating postoperative pain in ambulatory surgeries., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Morphine and oxycodone are potent opioid analgesics most commonly used for the management of moderate to severe acute and chronic pain. Their clinical utility is limited by undesired side effects like analgesic tolerance, dependence, and withdrawal. We have previously demonstrated that endothelin-A (ETA) receptor antagonists potentiate opioid analgesia and eliminate analgesic tolerance. Mechanistically, G proteins and regulatory proteins such as β-arrestins have shown to play an important role in mediating opioid tolerance, dependence, and withdrawal. Recently, the involvement of central ET mechanisms in opioid withdrawal was investigated. ETA receptor antagonist was shown to block majority of the signs and symptoms associated with opioid withdrawal. This review focuses on ET as one of the potential novel strategies to manage the challenge of opioid withdrawal. An overview of additional players in this process (G proteins and β-arrestin2), and the possible therapeutic implications of these findings are presented., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Objectives: Centhaquin citrate is a novel agent that is being developed for use in the resuscitation of patients with haemorrhagic shock. While pharmacokinetics have been described in small animal models, the pharmacokinetic parameters of centhaquin citrate in large mammals have yet to be described., Methods: Four healthy Beagle dogs (two males and two females) were given an intravenous bolus of 1.0 mg/kg centhaquin citrate. Plasma concentrations were measured at baseline and at ten time points within 24 h after administration. Multiple compartmental models were built and compared. The nonparametric adaptive grid function within the Pmetrics package for R was used for parameter estimation. Predicted concentrations were calculated using population mean and individual Bayesian posterior parameters., Key Findings: Centhaquin citrate pharmacokinetic parameters were best described using a two-compartment model. Median (IQR) values for Ke , Vc , Vp , Kcp and Kpc were 4.9 (4.4-5.2) h(-1) , 328.4 (304.0-331.9) l, 1000.6 (912.3-1042.4) l, 10.6 (10.3-11.1) h(-1) and 3.2 (2.9-3.7) h(-1) , respectively., Conclusions: Pharmacokinetic parameters of centhaquin citrate in a large mammal have been described. A large volume of distribution and rapid elimination were observed, consistent with previous work in rats., (© 2016 Royal Pharmaceutical Society.)

Centhaquin is a compound that produces hypotension and bradycardia in higher doses and resuscitation in lower doses. It is water insoluble, and is unsuitable for intravenous use. We prepared the citrate salt of centhaquin and evaluated its cardiovascular efficacy vs. centhaquin. Centhaquin citrate was prepared and characterized; its purity was determined by HPLC. Mean arterial pressure (MAP), heart rate (HR), pulse pressure (PP), cardiac output (CO), stroke volume (SV) and stroke work (SW) following intravenous administration of centhaquin and the citrate (0.05, 0.15 and 0.45 mg.kg(-1)) were determined in anaesthetized male Sprague-Dawley rats. Centhaquin citrate was 99.8% pure and water soluble. Centhaquin (0.05, 0.15 and 0.45 mg.kg(-1)) produced a maximal decrease in MAP of 15.6, 25.2 and 28.1%, respectively; while centhaquin citrate produced a greater (p<0.001) decrease of 35.7, 47.1 and 54.3%, respectively. The decrease in PP and HR produced by the citrate was greater than centhaquin (p<0.001). At 0.45 mg.kg(-1) centhaquin produced a maximal decrease of 20.9% (p<0.01) in CO, while centhaquin citrate produced a decrease of 42.1% (p<0.001). Reduction in SV (p<0.01) and SW (p<0.001) produced by centhaquin citrate were greater than centhaquin. Centhaquin citrate has greater cardiovascular activity compared to centhaquin., (© Georg Thieme Verlag KG Stuttgart · New York.)

The goals of this study, were to synthesize N-phenyl-N-(1-(2-(thiophen-2-yl)ethyl)azepane-4-yl)propionamide (1c) and determine its antinociceptive properties. The effect of clonidine on 1c antinociception and the involvement of opioid, α2-adrenergic, and I2 imidazoline receptors in 1c antinociception were studied. Also examined was the effect of an endothelin ETA receptor antagonist on 1c antinociception. Synthesis of 1c was accomplished in two steps using modifications of previously reported methods. Antinociceptive (tail-flick and hot-plate) latencies were measured in male Swiss Webster mice treated with 1c; antagonists+1c; clonidine+1c; or antagonists+clonidine+1c. Mice were pretreated with naloxone (opioid antagonist), yohimbine (α2-adrenoceptor antagonist), idazoxan (α2-adrenoceptor/I2-imidazoline antagonist), BU224 (I2-imidazoline antagonist) or BQ123 (endothelin ETA receptor antagonist) to study the involvement of these receptors. Compound 1c produced a dose-dependent increase in antinociceptive latencies; ED50 values were 0.15 mg/kg and 0.16 mg/kg, respectively, in the tail flick and hot plate tests. Naloxone, but not yohimbine, idazoxan or BU224, blocked 1c antinociception. Neither clonidine nor BQ123 potentiated 1c antinociception. Results demonstrate that 1c is 15-times more potent than morphine. The antinociceptive effect of 1c is mediated through opioid receptors. The α2-adrenergic, I2-imidazoline and endothelin ETA receptors are not involved in 1c antinociception., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Potentiation of opioid analgesia by endothelin-A (ET(A)) receptor antagonist, BMS182874, and imidazoline receptor/α₂-adrenoceptor agonists such as clonidine and agmatine are well known. It is also known that agmatine blocks morphine hyperthermia in rats. However, the effect of agmatine on morphine or oxycodone hypothermia in mice is unknown. The present study was carried out to study the role of α₂-adrenoceptors, imidazoline, and ET(A) receptors in morphine and oxycodone hypothermia in mice. Body temperature was determined over 6 h in male Swiss Webster mice treated with morphine, oxycodone, agmatine, and combination of agmatine with morphine or oxycodone. Yohimbine, idazoxan, and BMS182874 were used to determine involvement of α₂-adrenoceptors, imidazoline, and ET(A) receptors, respectively. Morphine and oxycodone produced significant hypothermia that was not affected by α₂-adrenoceptor antagonist yohimbine, imidazoline receptor/α₂ adrenoceptor antagonist idazoxan, or ET(A) receptor antagonist, BMS182874. Agmatine did not produce hypothermia; however, it blocked oxycodone but not morphine-induced hypothermia. Agmatine-induced blockade of oxycodone hypothermia was inhibited by idazoxan and yohimbine. The blockade by idazoxan was more pronounced compared with yohimbine. Combined administration of BMS182874 and agmatine did not produce changes in body temperature in mice. However, when BMS182874 was administered along with agmatine and oxycodone, it blocked agmatine-induced reversal of oxycodone hypothermia. This is the first report demonstrating that agmatine does not affect morphine hypothermia in mice, but reverses oxycodone hypothermia. Imidazoline receptors and α₂-adrenoceptors are involved in agmatine-induced reversal of oxycodone hypothermia. Our findings also suggest that ET(A) receptors may be involved in blockade of oxycodone hypothermia by agmatine., (© 2012 The Authors Fundamental and Clinical Pharmacology © 2012 Société Française de Pharmacologie et de Thérapeutique.)

The use of clonidine as a primary and adjuvant analgesic is well-documented. It is known that imidazoline and α2-adrenoceptors are involved in clonidine antinociception. Clonidine also produces antihypertensive actions mediated through the central nervous system. We have reported that centhaquin, a centrally-acting anti-hypertensive drug produces its hypotensive effect through a mechanism of action similar to clonidine. Centhaquin has also been shown to possess significant antinociceptive activity. Centhaquin antinociception is partially blocked by yohimbine, idazoxan, and naloxone; however, the involvement of specific adrenoceptor subtypes (α2A, α2B, or α2C) in centhaquin antinociception is unknown. The present study was conducted to determine antinociceptive properties of centhaquin citrate, a water soluble salt of centhaquin, and involvement of α2A-, α2B-, or α2C-adrenoceptors in centhaquin citrate antinociception in mice. BRL-44408 (α2A-adrenoceptor antagonist), imiloxan (α2B-adrenoceptor antagonist) and JP-1302 (α2C-adrenoceptor antagonist) were used to determine the involvement of α2A-, α2B-, or α2C-adrenoceptors, respectively. Antinociceptive (tail-flick and hot-plate) latencies were determined in male Swiss-Webster mice treated with centhaquin citrate alone and in combination with BRL-44408, imiloxan, or JP-1302. Centhaquin citrate produced significant antinociception in mice (P<0.05) which was unaffected by JP-1302 (P>0.05) but blocked by BRL-44408 (tail-flick test: 49.75% decrease, P<0.05; hot-plate test: 49.12% decrease, P<0.05) and imiloxan (tail-flick test: 46.98% decrease, P<0.05; hot-plate test: 46.42% decrease, P<0.05). This is the first report demonstrating centhaquin citrate antinociception and its blockade by BRL-44408 and imiloxan. We conclude that α2A and α2B but not α2C adrenoceptors are involved in centhaquin antinociception in mice., (© 2013 Elsevier B.V. All rights reserved.)

The potentiation of oxycodone antinociception by BMS182874 (endothelin-A (ET(A)) receptor antagonist) and agmatine (imidazoline receptor/α(2)-adrenoceptor agonist) is well-documented. It is also known that imidazoline receptors but not α(2)-adrenoceptors are involved in potentiation of oxycodone antinociception by agmatine and BMS182874 in mice. However, the involvement of specific imidazoline receptor subtypes (I(1), I(2), or both) in this interaction is not clearly understood. The present study was conducted to determine the involvement of imidazoline I(1) and I(2) receptors in agmatine- and BMS182874-induced potentiation of oxycodone antinociception in mice. Antinociceptive (tail flick and hot-plate) latencies were determined in male Swiss Webster mice treated with oxycodone, agmatine, BMS182874, and combined administration of oxycodone with agmatine or BMS182874. Efaroxan (imidazoline I(1) receptor antagonist) and BU224 (imidazoline I(2) receptor antagonist) were used to determine the involvement of I(1) and I(2) imidazoline receptors, respectively. Oxycodone produced significant antinociceptive response in mice which was not affected by efaroxan but was blocked by BU224. Agmatine-induced potentiation of oxycodone antinociception was blocked by BU224 but not by efaroxan. Similarly, BMS182874-induced potentiation of oxycodone antinociception was blocked by BU224 but not by efaroxan. This is the first report demonstrating that BMS182874- or agmatine-induced enhancement of oxycodone antinociception is blocked by BU224 but not by efaroxan. We conclude that imidazoline I(2) receptors but not imidazoline I(1) receptors are involved in BMS182874- and agmatine-induced potentiation of oxycodone antinociception in mice., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Kratom (Mitragyna speciosa) is a plant indigenous to Thailand and Southeast Asia. Kratom leaves produce complex stimulant and opioid-like analgesic effects. In Asia, kratom has been used to stave off fatigue and to manage pain, diarrhea, cough, and opioid withdrawal. Recently, kratom has become widely available in the United States and Europe by means of smoke shops and the Internet. Analyses of the medical literature and select Internet sites indicate that individuals in the United States are increasingly using kratom for the self-management of pain and opioid withdrawal. Kratom contains pharmacologically active constituents, most notably mitragynine and 7-hydroxymitragynine. Kratom is illegal in many countries. Although it is still legal in the United States, the US Drug Enforcement Administration has placed kratom on its "Drugs and Chemicals of Concern" list. Physicians should be aware of the availability, user habits, and health effects of kratom. Further research on the therapeutic uses, toxic effects, and abuse potential of kratom and its constituent compounds are needed.

Tramadol is a centrally acting analgesic that acts via μ-opioid agonism and by blocking the neuronal uptake of norepinephrine and serotonin. Clonidine potentiates the antinociceptive effects of tramadol; however the receptors involved in this potentiation have not been studied. Endothelin ET(A) receptor antagonists potentiate antinociceptive effects of morphine and oxycodone; however the effects of endothelin ET(A) receptor antagonists on tramadol antinociception have not been evaluated. This study was conducted to determine the effect of clonidine on tramadol antinociception; the role of opioid, α₂-adrenergic and I₂-imidazoline receptors in clonidine potentiation of tramadol antinociception; and the effect of endothelin ET(A) receptor antagonists in modulating tramadol antinociception. Antinociceptive (tail-flick and hot-plate) latencies were measured in male Swiss Webster mice treated with tramadol; clonidine plus tramadol; or antagonists plus tramadol. Mice were pretreated with naloxone (opioid antagonist), yohimbine (α₂-adrenoceptor antagonist), idazoxan (α₂-adrenoceptor/I₂-imidazoline antagonist), BMS182874 or BQ123 (endothelin ET(A) receptor antagonists) to study the involvement of these receptors. Tramadol produced a dose dependent increase in antinociceptive latencies. Tramadol antinociception was partially blocked by naloxone but not by yohimbine or idazoxan. Clonidine potentiated tramadol antinociception; potentiation was blocked by naloxone, yohimbine and idazoxan. Idazoxan produced a more pronounced blockade of potentiation than yohimbine. BMS182874 or BQ123 had no effect on tramadol antinociception, indicating that endothelin ET(A) receptors are not involved in tramadol antinociception in mice. Results demonstrate the involvement of opioid but not α₂-adrenergic/I₂-imidazoline receptors in tramadol antinociception and that opioid, α₂-adrenergic and I₂-imidazoline receptors are involved in clonidine potentiation of tramadol antinociception., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Objectives: The potentiation of morphine or oxycodone analgesia by endothelin-A (ET(A)) receptor antagonists and imidazoline/α(2)-adrenergic agonists is well documented. However, the effect of morphine or oxycodone in combination with an ET(A) receptor antagonist or an imidazoline/α(2) adrenergic agonist on body temperature is not known. The present study was carried out to study the role of ET(A) and imidazoline/α(2) adrenergic receptors in body temperature effects of morphine, oxycodone, and clonidine in rats., Methods: Body temperature was determined in male Sprague-Dawley rats treated with morphine, oxycodone, or clonidine. Yohimbine, idazoxan, and BMS182874 were used to determine the involvement of α(2)-adrenergic, imidazoline, and ET(A) receptors, respectively., Key Findings: Morphine and oxycodone produced hyperthermia which was not affected by α(2)-adrenergic antagonist yohimbine, imidazoline/α(2)-adrenergic antagonist idazoxan, or ET(A) receptor antagonist BMS182874. Clonidine alone produced hypothermia that was comparable to the hypothermia observed with clonidine plus morphine or oxycodone. The hypothermic effect of clonidine was blocked by idazoxan and yohimbine. The blockade by idazoxan was more pronounced compared to yohimbine. Clonidine hypothermia was not affected by BMS182874., Conclusions: This is the first report demonstrating that ET(A) receptors do not influence morphine- and oxycodone- induced hyperthermia or clonidine-induced hypothermia. Imidazoline receptors and α(2)-adrenergic receptors are involved in clonidine-induced hypothermia, but not in morphine- and oxycodone-induced hyperthermia., (Copyright © 2011 S. Karger AG, Basel.)

Background: Centhaquin is a centrally acting hypotensive drug like clonidine. Clonidine also produces analgesia and hypothermia in mice and potentiates morphine analgesia. Clonidine analgesia is blocked by idazoxan and naloxone while it is potentiated by BQ123 and sulfisoxazole. This study was conducted to determine the analgesic and hypothermic properties of centhaquin, and to assess whether it potentiates morphine analgesia. Yohimbine (α(2)-adrenergic antagonist), idazoxan (imidazoline/α(2)-adrenergic antagonist), naloxone (opioid antagonist), and BQ123 and sulfisoxazole (endothelin ET(A) antagonists) were used to study the involvement of these receptors in centhaquin analgesia and hypothermia., Methods: Analgesic (tail flick and hot-plate tests) latencies and body temperatures were measured in male Swiss Webster mice treated with vehicle plus centhaquin, antagonists plus centhaquin or centhaquin plus morphine., Results: Centhaquin produced dose-dependent analgesia which was partially blocked by yohimbine, idazoxan and naloxone. BQ123 and sulfisoxazole did not affect centhaquin analgesia. Morphine analgesia was not potentiated by centhaquin. Centhaquin produced mild hypothermia which was not blocked by yohimbine, idazoxan, naloxone, BQ123 or sulfisoxazole., Conclusions: This is the first report demonstrating the analgesic activity of centhaquin. The α(2)-adrenergic, imidazoline and opioid receptors are involved in mediating centhaquin analgesia. Endothelin ET(A) receptors do not play a role in centhaquin analgesia; centhaquin does not augment morphine analgesia., (Copyright © 2011 S. Karger AG, Basel.)

Clonidine, an alpha2-adrenergic agonist, has been demonstrated to produce significant analgesia and potentiate morphine analgesia. Endothelin (ETA) receptor antagonists have also been found to potentiate the antinociceptive response to morphine. Clonidine and ET have been reported to have cardiovascular interactions involving the sympathetic nervous system, but it is not known whether ETA receptor antagonist affects clonidine analgesia. This study examined the influence of sulfisoxazole (ETA receptor antagonist) on clonidine analgesia. Male Swiss Webster mice were used to determine antinociceptive response of drugs by measuring tail-flick latency. The effect of clonidine (0.3, 1.0, and 3.0 mg/kg, i.p.) alone or in combination with sulfisoxazole (25, 75, and 225 mg/kg, p.o.) on analgesia and body temperature was determined. Clonidine produced a dose-dependent analgesia and hypothermia. Sulfisoxazole (25, 75, and 225 mg/kg), when administered with clonidine (0.3 mg/kg), significantly potentiated (31% increase in area under the curve (AUC)) the analgesic effect of clonidine. Yohimbine (alpha2-adrenergic receptor antagonist) did not affect analgesic effect of clonidine plus sulfisoxazole. Idazoxan (I1-imidazoline and alpha2-adrenergic receptor antagonist) reduced (47% decrease in AUC) the analgesic effect of clonidine plus sulfisoxazole. Treatment with naloxone reduced (46% decrease in AUC) the analgesic effect of clonidine plus sulfisoxazole. The effect of another ETA receptor antagonist, BMS-182874 (2, 10, and 50 microg, i.c.v.) was studied, and it was found that the dose of 10 microg significantly potentiated (26% increase in AUC) the analgesic effect of clonidine. These results indicate that sulfisoxazole, an ETA receptor antagonist, potentiates the analgesic effect of clonidine, which could be mediated through I1-imidazoline receptors and opioid receptors.

Background: Numerous agents have been demonstrated to potentiate morphine analgesia, including clonidine (alpha(2)-adrenergic and I(1)-imidazoline receptor agonist) and BMS182874 (endothelin-A, ET(A,) receptor antagonist). ET has been shown to affect pharmacological actions of clonidine. The present study was conducted to determine whether alpha(2)-adrenergic and/or I(1)-imidazoline receptors are involved in the augmentation of morphine and oxycodone analgesia by clonidine and BMS182874., Methods: Analgesic tail flick latencies were measured in rats at various time intervals, and were converted to AUC(0)-->(360 min)., Results: It was found that clonidine produced mild analgesia, while BMS182874 did not have any analgesic effect. Clonidine (p = 0.015) and BMS182874 (p = 0.009) enhanced the analgesic action of morphine and oxycodone. Clonidine- or BMS182874-induced increases in the analgesic effect of morphine were not inhibited by idazoxan (I(1)-imidazoline receptor antagonist), while increases in the analgesic effect of oxycodone were blocked by idazoxan. Yohimbine (alpha(2)-adrenergic receptor antagonist) blocked the clonidine-induced potentiation of analgesic effect of morphine (p = 0.036) and oxycodone (p = 0.0167), while yohimbine did not affect BMS182874-induced potentiation of the analgesic effect of morphine or oxycodone., Conclusions: This is the first report showing that clonidine and BMS182874 augment oxycodone analgesia. Results suggest that alpha(2)-adrenergic receptors are involved in clonidine-induced, but not in the BMS182874-induced, potentiation of the analgesic effects of morphine or oxycodone, and that I(1)-imidazoline receptors are involved in the potentiation of oxycodone analgesia, but not morphine analgesia, by clonidine and BMS182874.

Gene therapy to the cornea can potentially correct inherited and acquired diseases of the cornea. Factors that facilitate corneal gene delivery are the accessibility and transparency of the cornea, its stability ex vivo and the immune privilege of the eye. Initial corneal gene delivery studies characterized the relationship between intraocular modes of administration and location of reporter gene expression. The challenge of achieving effective topical gene transfer, presumably due to tear flow, blinking and low penetration of the vector through epithlelial tight junctions left no alternative but invasive administration to the anterior chamber and corneal stroma. DNA vaccination, RNA interference and gene transfer of cytokines, growth factors and enzymes modulated the corneal microenvironment. Positive results were obtained in preclinical studies for prevention and treatment of corneal graft rejection, neovascularization, haze and herpetic stromal keratitis. These studies, corneal gene delivery systems and modes of administration, and considerations regarding the choice of animal species used are the focus of this review. Opportunities in the field of corneal gene therapy lie in expanding the array of corneal diseases investigated and in the implementation of recent designs of safer vectors with reduced immunogenicity and longer duration of gene expression.

We have reported that functionalized amino acids (FAA) are potent anticonvulsants. Replacing the N-terminal amide group in FAA with phenethyl, styryl, and phenylethynyl units provided a series of functionalized amido ketones (FAK). We show that select FAK exhibit significant anticonvulsant activities thereby providing information about the structural requirements for FAA and FAK bioactivity.

We have reported that functionalized amino acids 1 display potent anticonvulsant activities in mice and rats, and that the activity resides primarily in the D-isomer. In this study we investigated whether selectively replacing the C(2) tetrahedral atom with a trivalent nitrogen provides compounds with comparable activity. Six functionalized N(2)-substituted semicarbazides (3) were prepared. X-ray crystallographic analysis of 1-acetyl-4-benzyl-2-(thiazol-2-yl)semicarbazide (13) showed that it lost asymmetry and adopted a configuration midway between the corresponding D- and L-amino acid derivatives. Evaluation of 3 in both mice (ip) and rats (po) showed that the compounds exhibited significant anticonvulsant activities but in most cases at levels lower than their amino acid counterparts. One of the semicarbazides, 13, displayed excellent activity in mice and rats that compared favorably to that of phenytoin.

We recently reported that the ED50 value for (R,S)-2,3-dimethoxypropionamide (1) in the maximal electroshock (MES)-induced seizure test in mice was 30 mg/kg (Choi, D.; Stables, J.P., Kohn, H. Bioorg. Med. Chem. 1996, 4, 2105). This value is comparable to that observed for phenobarbital (ED50 = 22 mg/kg). Compound 1 is structurally similar to a class of MES-selective anticonvulsant agents, termed functionalized amino acids (2), that were developed in our laboratory. The distinguishing feature of 2 is the differential activities observed for enantiomers. In this study, we asked whether comparable differences in activities were observed in the MES-induced seizure test for (R)- and (S)-1. We developed stereospecific syntheses for these enantiomers and showed that both compounds exhibit nearly equal anticonvulsant activity in mice (i.p.) (MES ED50 = 79-111 mg/kg). The surprisingly high ED50 values for (R)- and (S)-1 required our redetermining the ED50 value for (R,S)-1. We revised this value to 79 mg/kg. A limited structure-activity relationship study for 1 was conducted. Special attention was given to the C(2) methoxy unit in 1. We found that replacement of this moiety led to only modest differences in the MES activities upon ip administration to mice. Significantly, we observed an enhancement in the anticonvulsant activity for (R,S)-N-benzyl 2-hydroxy-3-methoxypropionamide ((R,S)-6) upon oral administration to rats ((R,S)-6: mice (i.p.) ED50 > 100, < 300 mg/kg; rat (oral) ED50 = 62 mg/kg). The activities of 3-methoxypropionamides, functionalized amino acids, and related compounds are discussed.

A sensitive, specific urinary assay for fentanyl, sufentanil, and alfentanil based on their N-dealkylated metabolites is described. Norfentanyl, norsufentanil-noralfentanil, and 2H5-norfentanyl are synthesized and characterized by standard analytical techniques. Derivatization of these secondary amines to yield the pentafluorobenzamides produces stable products with good gas chromatographic properties and unique, high-mass fragments in their mass spectra. These properties are utilized to develop a drug screening procedure based on gas chromatography-mass spectrometry to detect these major metabolites in human urine. The metabolites are isolated from urine samples by a liquid-liquid extraction procedure. The method allows for detection of metabolite concentrations as low as 0.3 ng/mL.