morphine and Neuralgia

We previously reported that a multifunctional opioid/neuropeptide FF receptor agonist, DN-9, achieved peripherally restricted analgesia with reduced side effects. To develop stable and orally bioavailable analogues of DN-9, eight lactam-bridged cyclic analogues of DN-9 between positions 2 and 5 were designed, synthesized, and biologically evaluated.

Topics: Analgesics, Opioid; Animals; Ligands; Male; Mice; Neuralgia; Peptides, Cyclic; Receptors, Neuropeptide

Herein, the opioid pharmacophore H-Dmt-d-Arg-Aba-β-Ala-NH2 (7) was linked to peptide ligands for the nociceptin receptor. Combination of 7 and NOP ligands (e.g., H-Arg-Tyr-Tyr-Arg-Ile-Lys-NH2) led to binding affinities in the low nanomolar domain. In vitro, the hybrids behaved as agonists at the opioid receptors and antagonists at the nociceptin receptor. Intravenous administration of hybrid 13a (H-Dmt-d-Arg-Aba-β-Ala-Arg-Tyr-Tyr-Arg-Ile-Lys-NH2) to mice resulted in potent and long lasting antinociception in the tail-flick test, indicating that 13a was able to permeate the BBB. This was further supported by a cell-based BBB model. All hybrids alleviated allodynia and hyperalgesia in neuropathic pain models. Especially with respect to hyperalgesia, they showed to be more effective than the parent compounds. Hybrid 13a did not result in significant respiratory depression, in contrast to an equipotent analgesic dose of morphine. These hybrids hence represent a promising avenue toward analgesics for the dual treatment of acute and neuropathic pain.

Topics: Acute Disease; Amino Acid Sequence; Animals; Behavior, Animal; Blood-Brain Barrier; Cell Membrane Permeability; Humans; Ligands; Male; Mice; Narcotic Antagonists; Neuralgia; Nociceptin Receptor; Pain Management; Peptides; Rats; Rats, Sprague-Dawley; Receptors, Opioid

Chemokine release promotes cross-talk between opioid and chemokine receptors that in part leads to reduced efficacy of morphine in the treatment of chronic pain. On the basis of the possibility that a MOR-CCR5 heteromer is involved in such cross-talk, we have synthesized bivalent ligands (MCC series) that contain mu opioid agonist and CCR5 antagonist pharmacophores linked through homologous spacers (14-24 atoms). When tested on lipopolysaccharide-inflamed mice, a member of the series (MCC22; 3e) with a 22-atom spacer exhibited profound antinociception (i.t. ED50 = 0.0146 pmol/mouse) that was 2000× greater than morphine. Moreover, MCC22 was ~3500× more potent than a mixture of mu agonist and CCR5 antagonist monovalent ligands. These data strongly suggest that MCC22 acts by bridging the protomers of a MOR-CCR5 heteromer having a TM5,6 interface. Molecular simulation studies are consistent with such bridging. This study supports the MOR-CCR5 heteromer as a novel target for the treatment of chronic pain.

Topics: Analgesics; Animals; CCR5 Receptor Antagonists; Chronic Disease; HEK293 Cells; Humans; Inflammation; Male; Mice; Models, Molecular; Molecular Targeted Therapy; Neuralgia; Receptors, CCR5; Receptors, Opioid, mu

In a previous communication, the SAR of a series of potent and selective 5-sulfonyl-benzimidazole CB2-receptor agonists was described. The lack of in vivo activity of compounds from this series was attributed to their poor solubility and metabolic stability. In this Letter, we report on the further optimization of this series, leading to the relatively polar and peripherically acting CB2 agonists 41 and 49. Although both compounds were not active in acute pain models, the less selective compound 41 displayed good, sustained activity in a chronic model of neuropathic pain without the tolerance observed with morphine. In addition, both 41 and 49 delayed the onset of clinical symptoms in an experimental model for Multiple sclerosis.

Topics: Animals; Benzimidazoles; Brain; Drug Design; Encephalomyelitis, Autoimmune, Experimental; Humans; Inflammation; Mice; Models, Chemical; Multiple Sclerosis; Neuralgia; Rats; Receptor, Cannabinoid, CB2; Structure-Activity Relationship; Time Factors

The endogenous opioid peptide endomorphin-1 (1) was modified by attachment of lactose to the N-terminus via a succinamic acid spacer to produce compound 2. The carbohydrate modification significantly improved the metabolic stability and membrane permeability of 2 while retaining μ-opioid receptor binding affinity and agonist activity. Analogue 2 produced dose-dependent antinociceptive activity following intravenous administration in a chronic constriction injury (CCI) rat model of neuropathic pain with an ED(50) of 8.3 (± 0.8) μmol/kg. The corresponding ED(50) for morphine was 2.6 (± 1.4) μmol/kg. Importantly, compound 2 produced dose-dependent pain relief after oral administration in CCI rats (ED(50) = 19.6 (± 1.2) μmol/kg), which was comparable with that of morphine (ED(50) = 20.7 (±3.6) μmol/kg). Antineuropathic effects of analogue 2 were significantly attenuated by pretreatment of animals with the opioid antagonist naloxone, confirming opioid receptor-mediated analgesia. In contrast to morphine, no significant constipation was produced by compound 2 after oral administration.

Topics: Absorption; Administration, Oral; Analgesics, Opioid; Animals; Chemistry Techniques, Synthetic; CHO Cells; Constipation; Cricetinae; Cricetulus; Glycosylation; Male; Naloxone; Narcotic Antagonists; Neuralgia; Oligopeptides; Rats; Rats, Sprague-Dawley; Receptors, Opioid

Current drugs for the treatment of seizure disorders, although effective in many patients, still suffer from a number of failures and are not effective in some forms of resistant epilepsies. Historically, many of these drugs have multiple mechanisms of action including calcium and sodium channel blockade as well as GABAergic activity and thus a number of associated side effects. Modulation of the M-current through opening of KCNQ channels has been proposed as a way to attenuate neuroexcitability and have a therapeutic benefit for the treatment of seizure disorders. Therefore, as part of our program to identify new treatments for epilepsy, we set out to identify agonists of KCNQ channels. High throughput screening of our corporate collection led to the identification of 1, adamantane-1-carboxylic acid (3-methyl-3H-benzothiazol-2-ylidine) hydrazide, a potent KCNQ2/Q3 agonist. Herein, we describe the syntheses and structure-activity relationships of analogues of 1 as well as their in vivo activity in animal models of epilepsy and neuropathic pain.

Topics: Adamantane; Animals; Azides; Epilepsy; KCNQ2 Potassium Channel; KCNQ3 Potassium Channel; Mice; Neuralgia; Structure-Activity Relationship

Sulfamoyl benzamides were identified as a novel series of cannabinoid receptor ligands. Starting from a screening hit 8 that had modest affinity for the cannabinoid CB(2) receptor, a parallel synthesis approach and initial SAR are described, leading to compound 27 with 120-fold functional selectivity for the CB(2) receptor. This compound produced robust antiallodynic activity in rodent models of postoperative pain and neuropathic pain without traditional cannabinergic side effects.

Topics: Animals; Benzamides; Binding Sites; Dose-Response Relationship, Drug; Ligands; Mice; Models, Animal; Models, Chemical; Neuralgia; Pain Measurement; Rats; Receptor, Cannabinoid, CB2; Structure-Activity Relationship; Sulfonamides