Manipulating Pharmacodynamic Efficacy with Agonist + Antagonist Mixtures: In Vitro and In Vivo Studies with Opioids and Cannabinoids

Selley, Dana E.; Banks, Matthew L.; Diester, Clare M; Jali, Abdul M; Legakis, Luke P; Santos, Edna J.; Negus, S. Stevens

doi:10.1124/jpet.120.000349

Cited by 8 publications

(27 citation statements)

References 27 publications

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“…Step 2 evaluated effects produced by a series of fixed-proportion fentanyl/naltrexone mixtures. We have reported previously that the proportion of fentanyl in fentanyl/naltrexone mixtures can be manipulated such that decreasing fentanyl proportions result in decreasing net efficacy of the mixture ( 36 , 38 – 40 ). Here, we examined 10:1, 3.2:1, and 1:1 mixtures of fentanyl/naltrexone.…”

Section: Methodsmentioning

confidence: 99%

“…A significant ANOVA was again followed by a Holm-Sidak post hoc test. Lastly, data from experiments with fentanyl/naltrexone mixtures administered alone were used to determine the efficacy requirement for opioid effects on climbing as we have described previously ( 36 , 38 – 40 ). Briefly, data from each mixture were transformed to a percent of the maximum effect produced by fentanyl alone using the equation [(vehicle - mixture) ÷ (vehicle – fentanyl)] ×100, where “vehicle” equals the mean vehicle control data in a group, “mixture” equals the time climbing in a given mouse after a given dose of a mixture, and “fentanyl” equals the mean maximum effect of fentanyl alone in the fentanyl treatment group.…”

Section: Methodsmentioning

confidence: 99%

“…MOR efficacy may be especially relevant for opioid effects in assays of pain-depressed behavior, where opioids can produce competing effects that include both analgesia (which alleviates pain-related behavioral depression and increases rates of the target behavior) and motor impairment (which can reduce rates of the target behavior and obscure analgesic restoration of pain-depressed behavior) ( 19 , 34 , 35 ). Accordingly, we manipulated MOR efficacy by testing both (a) a set of single-molecule opioids with decreasing MOR efficacy (fentanyl > buprenorphine > naltrexone) ( 34 , 36 , 37 ), and (b) a series of fixed-proportion fentanyl/naltrexone mixtures that vary in net MOR efficacy as described previously ( 36 , 38 – 40 ). We hypothesized that low-efficacy single-molecule opioids or fentanyl/naltrexone mixtures would have sufficient efficacy to alleviate pain-related depression of climbing without affecting motor behavior.…”

Section: Introductionmentioning

confidence: 99%

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Climbing behavior by mice as an endpoint for preclinical assessment of drug effects in the absence and presence of pain

et al. 2023

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This study evaluated climbing in mice as a tool to assess the expression and treatment of pain-related behavioral depression in male and female ICR mice. Mice were videotaped during 10-min sessions in a vertical plexiglass cylinder with wire mesh walls, and “Time Climbing” was scored by observers blind to treatments. Initial validation studies demonstrated that baseline climbing was stable across repeated days of testing and depressed by intraperitoneal injection of dilute lactic acid (IP acid) as an acute pain stimulus. Additionally, IP acid-induced depression of climbing was blocked by the positive-control non-steroidal anti-inflammatory drug (NSAID) ketoprofen but not by the negative control kappa opioid receptor agonist U69593. Subsequent studies examined effects of single-molecule opioids (fentanyl, buprenorphine, naltrexone) and of fixed-proportion fentanyl/naltrexone mixtures (10:1, 3.2:1, and 1:1) that vary in their efficacy at the mu opioid receptor (MOR). Opioids administered alone produced a dose- and efficacy-dependent decrease in climbing, and fentanyl/naltrexone-mixture data indicated that climbing in mice is especially sensitive to disruption by even low-efficacy MOR activation. Opioids administered as a pretreatment to IP acid failed to block IP acid-induced depression of climbing. Taken together, these findings support the utility of climbing in mice as an endpoint to evaluate candidate-analgesic effectiveness both to (a) produce undesirable behavioral disruption when the test drug is administered alone, and (b) produce a therapeutic blockade of pain-related behavioral depression. The failure of MOR agonists to block IP acid-induced depression of climbing likely reflects the high sensitivity of climbing to disruption by MOR agonists.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Climbing behavior by mice as an endpoint for preclinical assessment of drug effects in the absence and presence of pain

et al. 2023

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“…Competition binding assays were performed as previously described [ 26 , 27 ]. Briefly, mMOR-CHO membrane homogenates containing 20 µg membrane protein were incubated with 1.4 nM [ 3 H]naloxone in the presence and absence of varying concentrations of test compounds in TME buffer (50 mM Tris, 3 mM MgCl 2 , and 0.2 mM EGTA, pH 7.7) for 1.5 h at 30 °C.…”

Section: Methodsmentioning

confidence: 99%

“…[ 35 S]GTPγS functional assays were performed as described [ 26 , 27 ]. Briefly, mMOR-CHO membrane homogenates containing 14 µg of membrane protein were incubated in TME buffer with 100 mM NaCl, 20 µM GDP, 0.1 nM [ 35 S]GTPγS with and without varying concentrations of test compounds in a final volume of 500 µL for 1.5 h at 30 °C.…”

Section: Methodsmentioning

confidence: 99%

A Journey through Diastereomeric Space: The Design, Synthesis, In Vitro and In Vivo Pharmacological Activity, and Molecular Modeling of Novel Potent Diastereomeric MOR Agonists and Antagonists

et al. 2022

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Four sets of diastereomeric C9-alkenyl 5-phenylmorphans, varying in the length of the C9-alkenyl chain, were designed to examine the effect of these spatially distinct ligands on opioid receptors. Functional activity was obtained by forskolin-induced cAMP accumulation assays and several compounds were examined in the [35S]GTPgS assay and in an assay for respiratory depression. In each of the four sets, similarities and differences were observed dependent on the length of their C9-alkenyl chain and, most importantly, their stereochemistry. Three MOR antagonists were found to be as or more potent than naltrexone and, unlike naltrexone, none had MOR, KOR, or DOR agonist activity. Several potent MOR full agonists were obtained, and, of particular interest partial agonists were found that exhibited less respiratory depression than that caused by morphine. The effect of stereochemistry and the length of the C9-alkenyl chain was also explored using molecular modeling. The MOR antagonists were found to interact with the inactive (4DKL) MOR crystal structures and agonists were found to interact with the active (6DDF) MOR crystal structures. The comparison of their binding modes at the mouse MOR was used to gain insight into the structural basis for their stereochemically induced pharmacological differences.

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Role of efficacy as a determinant of locomotor activation by mu‐opioid receptor (MOR) ligands in female and male mice. II. Effects of novel MOR‐selective phenylmorphans with high‐to‐low MOR efficacy

Santos

Nassehi

Bow³

et al. 2023

Pharmacology Res & Perspec

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Low‐efficacy mu‐opioid receptor (MOR) agonists represent promising therapeutics, but existing compounds (e.g., buprenorphine, nalbuphine) span a limited range of low MOR efficacies and have poor MOR selectivity. Accordingly, new and selective low‐efficacy MOR agonists are of interest. A novel set of chiral C9‐substituted phenylmorphans has been reported to display improved MOR selectivity and a range of high‐to‐low MOR efficacies under other conditions; however, a full opioid receptor binding profile for these drugs has not been described. Additionally, studies in mice will be useful for preclinical characterization of these novel compounds, but the pharmacology of these drugs in mice has also not been examined. Accordingly, the present study characterized the binding selectivity and in vitro efficacy of these compounds using assays of opioid receptor binding and ligand‐stimulated [35S]GTPɣS binding. Additionally, locomotor effects were evaluated as a first step for in vivo behavioral assessment in mice. The high‐efficacy MOR agonist and clinically effective antidepressant tianeptine was included as a comparator. In binding studies, all phenylmorphans showed improved MOR selectivity relative to existing lower‐efficacy MOR agonists. In the ligand‐stimulated [35S]GTPɣS binding assay, seven phenylmorphans had graded levels of sub‐buprenorphine MOR efficacy. In locomotor studies, the compounds again showed graded efficacy with a rapid onset and ≥1 h duration of effects, evidence for MOR mediation, and minor sex differences. Tianeptine functioned as a high‐efficacy MOR agonist. Overall, these in vitro and in vivo studies support the characterization of these compounds as MOR‐selective ligands with graded MOR efficacy and utility for further behavioral studies in mice.

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Manipulating Pharmacodynamic Efficacy with Agonist + Antagonist Mixtures: In Vitro and In Vivo Studies with Opioids and Cannabinoids

Cited by 8 publications

References 27 publications

Climbing behavior by mice as an endpoint for preclinical assessment of drug effects in the absence and presence of pain

Climbing behavior by mice as an endpoint for preclinical assessment of drug effects in the absence and presence of pain

A Journey through Diastereomeric Space: The Design, Synthesis, In Vitro and In Vivo Pharmacological Activity, and Molecular Modeling of Novel Potent Diastereomeric MOR Agonists and Antagonists

Role of efficacy as a determinant of locomotor activation by mu‐opioid receptor (MOR) ligands in female and male mice. II. Effects of novel MOR‐selective phenylmorphans with high‐to‐low MOR efficacy

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