ABSTRACT
A new series of CB2-selective agonists containing a benzimidazole core is reported. Design, synthesis, SAR and pharmacokinetic data for selected compounds are described.
Subject(s)
Benzimidazoles/pharmacology , Drug Design , Receptor, Cannabinoid, CB2/agonists , Benzimidazoles/chemical synthesis , Benzimidazoles/chemistry , Dose-Response Relationship, Drug , Humans , Models, Molecular , Molecular Structure , Structure-Activity RelationshipABSTRACT
A novel series of decahydroquinoline CB2 agonists is described. Optimization of the amide substituent led to improvements in CB2/CB1 selectivity as well as physical properties. Two key compounds were examined in the rat CFA model of acute inflammatory pain. A moderately selective CB2 agonist was active in this model. A CB2 agonist lacking functional CB1 activity was inactive in this model despite high in vivo exposure both peripherally and centrally.
Subject(s)
Amides/chemistry , Analgesics/chemistry , Quinolines/chemistry , Receptor, Cannabinoid, CB2/agonists , Amides/chemical synthesis , Amides/therapeutic use , Analgesics/chemical synthesis , Analgesics/therapeutic use , Animals , Disease Models, Animal , Humans , Mice , Mice, Transgenic , Pain/drug therapy , Rats , Receptor, Cannabinoid, CB1/agonists , Receptor, Cannabinoid, CB1/metabolism , Receptor, Cannabinoid, CB2/metabolism , Structure-Activity RelationshipABSTRACT
A new series of imidazopyridine CB2 agonists is described. Structural optimization improved CB2/CB1 selectivity in this series and conferred physical properties that facilitated high in vivo exposure, both centrally and peripherally. Administration of a highly selective CB2 agonist in a rat model of analgesia was ineffective despite substantial CNS exposure, while administration of a moderately selective CB2/CB1 agonist exhibited significant analgesic effects.
Subject(s)
Analgesics/chemistry , Pyridines/chemistry , Receptor, Cannabinoid, CB1/agonists , Receptor, Cannabinoid, CB2/agonists , Analgesics/chemical synthesis , Analgesics/therapeutic use , Animals , Disease Models, Animal , Freund's Adjuvant/pharmacology , Humans , Hyperalgesia/drug therapy , Pyridines/chemical synthesis , Pyridines/therapeutic use , Rats , Receptor, Cannabinoid, CB1/metabolism , Receptor, Cannabinoid, CB2/metabolismABSTRACT
We established HEK-293 cell lines that stably express functional canine ether-à-go-go-related gene (cERG) K(+) channels and examined their biophysical and pharmacological properties with whole cell patch clamp and (35)S-labeled MK-499 ([(35)S]MK-499) binding displacement. Functionally, cERG current had the hallmarks of cardiac delayed rectifier K(+) current (I(Kr)). Channel opening was time- and voltage dependent with threshold near -40 mV. The half-maximum activation voltage was -7.8 +/- 2.4 mV at 23 degrees C, shifting to -31.9 +/- 1.2 mV at 36 degrees C. Channels activated with a time constant of 13 +/- 1 ms at +20 mV, showed prominent inward rectification at depolarized potentials, were highly K(+) selective (Na(+)-to-K(+) permeability ratio = 0.007), and were potently inhibited by I(Kr) blockers. Astemizole, terfenadine, cisapride, and MK-499 inhibited cERG and human ERG (hERG) currents with IC(50) values of 1.3, 13, 19, and 15 nM and 1.2, 9, 14, and 21 nM, respectively, and competitively displaced [(35)S]MK-499 binding from cERG and hERG with IC(50) values of 0.4, 12, 35, and 0.6 nM and 0.8, 5, 47, and 0.7 nM, respectively. cERG channels had biophysical properties appropriate for canine action potential repolarization and were pharmacologically sensitive to agents known to prolong QT. A novel MK-499 binding assay provides a new tool to detect agents affecting ERG channels.
Subject(s)
Dogs/physiology , Potassium Channel Blockers/pharmacology , Potassium Channels, Voltage-Gated , Potassium Channels/drug effects , Potassium Channels/physiology , Animals , Benzopyrans/metabolism , Benzopyrans/pharmacology , Binding, Competitive , Blotting, Western , Cell Line , ERG1 Potassium Channel , Electric Conductivity , Ether-A-Go-Go Potassium Channels , Humans , Immunologic Techniques , Ion Channel Gating , Kinetics , Patch-Clamp Techniques , Piperidines/metabolism , Piperidines/pharmacology , Potassium/metabolism , Staining and Labeling , TemperatureABSTRACT
BACKGROUND: Neurons in the dorsal spinal cord play important roles in nociception and pain. These neurons receive input from peripheral sensory neurons and then transmit the signals to the brain, as well as receive and integrate descending control signals from the brain. Many molecules important for pain transmission have been demonstrated to be localized to the dorsal horn of the spinal cord. Further understanding of the molecular interactions and signaling pathways in the dorsal horn neurons will require a better knowledge of the molecular neuroanatomy in the dorsal spinal cord. RESULTS: A large scale screening was conducted for genes with enriched expression in the dorsal spinal cord using DNA microarray and quantitative real-time PCR. In addition to genes known to be specifically expressed in the dorsal spinal cord, other neuropeptides, receptors, ion channels, and signaling molecules were also found enriched in the dorsal spinal cord. In situ hybridization and immunohistochemistry revealed the cellular expression of a subset of these genes. The regulation of a subset of the genes was also studied in the spinal nerve ligation (SNL) neuropathic pain model. In general, we found that the genes that are enriched in the dorsal spinal cord were not among those found to be up-regulated in the spinal nerve ligation model of neuropathic pain. This study also provides a level of validation of the use of DNA microarrays in conjunction with our novel analysis algorithm (SAFER) for the identification of differences in gene expression. CONCLUSION: This study identified molecules that are enriched in the dorsal horn of the spinal cord and provided a molecular neuroanatomy in the spinal cord, which will aid in the understanding of the molecular mechanisms important in nociception and pain.
