Antihyperalgesic effect of [(±)-(2,4,6-cis)-4-chloro-6-(naphthalen-1-yl)-tetrahydro-2H-pyran-2-yl]methanol: participation of the NO/cGMP/KATP pathway and κ-opioid receptor

Evaluation of the systemic and spinal antinociceptive effect of a new hybrid NSAID tetrahydropyran derivative

Pain is responsible for inducing physical and mental stress, interfering negatively in patients' quality of life. Classic analgesic drugs, such as opioids and non-steroidal anti-inflammatory drugs, are known for their wide range of adverse effects, making it important to develop new drugs. Thus, this study aimed to analyse the action of the hybrid compound cis- (±) -acetate of 4-chloro-6- (naphthalene-1-yl) -tetrahydro-2h-pyran -2-yl) methyl2- (2- [2,6-dichlorophenylamine] phenyl (LS19) under acute nociceptive conditions, and deepened the understanding of the responsible mechanisms. Male Swiss mice were evaluated in the acetic acid-induced abdominal writhing, formalin, tail flick, capsaicin- and glutamate-induced nociception, thermal stimulation in animals injected with capsaicin and rotarod tests besides the acute and subchronic toxicological evaluation. The compound showed effect on the acetic acid-induced abdominal writhing, formalin (both phases), tail flick, thermal stimulation in animals injected with capsaicin and capsaicin-induced nociception tests. In the study of the mechanism of action was observed reversion of the antihyperalgesic effect of the compound from the previous intraperitoneal and intrathecal administration of naloxone, nor-binaltorphimine, naltrindole, methylnaltrexone, 7-nitroindazole, L-NAME, ODQ, glibenclamide on the tail flick test. In the thermal stimulation in animals injected with capsaicin, the compound showed antinociceptive effect by oral and intraplantar routes, besides to reducing the levels of TNF-α, IL-1β and PGE2 in the paws previously administered with capsaicin. There were no signs of acute and subchronic intoxication with the compound. In summary, the compound LS19 presented spinal and local antihyperalgesic effect, demonstrating participation of the opioid/NO/cGMP/K+ ATP pathway and TRPV1 receptors and it demonstrated safety in its use in mice.

Endogenous opiates and behavior: 2017

This paper is the fortieth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2017 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Pharmacological evaluation underlying the antinociceptive activity of two new hybrids NSAIDs tetrahydropyran derivatives

The development of analgesic drugs is still a necessity due to the inefficiency of the current treatments for some pathological conditions and also due to the adverse effects produced by these drugs. The aim of this study was to deepen the pharmacological study of two new hybrids NSAIDs tetrahydropyran derivatives, regarding their antinociceptive effects on acute pain in mice. Male swiss mice were evaluated in the acetic acid-induced abdominal writhing, formalin, tail-flick, open-field, glutamate- and capsaicin-induced paw licking tests, and in vitro Cox inhibition assay, besides the acute toxicological evaluation. The compounds had an effect on the acetic acid-induced abdominal writhing, formalin (both phases), and tail-flick tests. In the study of the mechanism of action was observed reversion of the antinociceptive effect of the compounds from the previous administration of naloxone, L-NAME (L-nitro-arginine methyl ester), ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one), glibenclamide, and nor-binaltorphimine, by the intrathecal and intraperitoneal routes. The prior administration of MK-801 suggests that the modulation of NMDA receptor contributes to the antinociceptive effect of compounds. In summary, hybrid compounds presented central antinociceptive effect, demonstrating participation of the NO-cGMP-K⁺ ATP pathway, κ-opioid, and NMDA receptors. In addition, the compounds showed inhibition of cyclo-oxygenase enzymes and adverse effects were not observed with dose 300 times greater than the dose used experimentally.

Synthesis of 16 New Hybrids from Tetrahydropyrans Derivatives and Morita-Baylis-Hillman Adducts: In Vitro Screening against Leishmania donovani

Leishmaniases are a group of neglected tropical diseases (NTDs) caused by protozoan parasites from >20 Leishmania species. Visceral leishmaniasis (VL), also known as kala-aza, is the most severe form of leishmaniasis, usually fatal in the absence of treatment in 95% of cases. The Morita-Baylis-Hillman adducts (MBHAs) are being explored as drug candidates against several diseases, one of them being leishmaniasis. We present here the design, synthesis and in vitro screening against Leishmania donovani of sixteen new molecular hybrids from analgesic/anti-inflammatory tetrahydropyrans derivatives and Morita-Baylis-Hillman adducts. First, acrylates were synthesized from analgesic/anti-inflammatory tetrahydropyrans using acrylic acid under TsOH as a catalyst (70%–75% yields). After the 16 new MBHAs were prepared in moderate to good yields (60%–95%) promoted by microwave irradiation or low temperature (0 °C) in protic and aprotic medium. The hybrids were evaluated in vitro on the promastigote stage of Leishmania donovani by determining their inhibitory concentrations 50% (IC₅₀), 50% hemolysis concentration (HC₅₀), selectivity index (HC₅₀/IC₅₀,), and comparing to Amphotericin B, chosen as the anti-leishmanial reference drug. The hybrid which presents the bromine atom in its chemical structure presents high leishmanicide activity and the high selectivity index in red blood cells (SI_rb > 180.19), compared with the highly-toxic reference drug (SI_rb = 33.05), indicating that the bromine hybrid is a promising compound for further biological studies.