Rationale TRV130 (oliceridine; N-[(3-methoxythiophen-2-yl)methyl]-2-[(9R)-9-pyridin-2-yl-6-oxaspiro[4.5]decan-9-yl]ethanamine) is a novel mu opioid receptor (MOR) agonist that preferentially activates G-protein vs. β-arrestin signaling pathways coupled to MORs. Prevailing evidence suggests that TRV130 and other G-protein-biased MOR agonists may produce therapeutic analgesic effects with reduced adverse effects compared to existing MOR agonists. Objectives This study compared effects of acute and repeated TRV130 administration on measures of antinociception, gastrointestinal function, and abuse liability in rodents. We hypothesized that TRV130 would produce robust and sustained antinociception and abuse-related effects during repeated treatment, but that tolerance would develop to GI inhibition. Methods Antinociception was assessed using a warm-water tail-withdrawal procedure in mice. Gastrointestinal function was assessed in mice using an in vivo measure of fecal output and in vitro assays of colonic propulsion and of colon and ileum circular muscle contraction. Abuse liability was assessed in rats using an intracranial self-stimulation (ICSS) procedure. (+)-TRV130 was administered with acute and repeated dosing regimens, and (−)-TRV130 was also examined in the ICSS procedure to assess stereoselectivity. Results Acute (+)-TRV130 treatment produced robust antinociception, complete inhibition of gastrointestinal function, and weak abuse-related effects. Repeated (+)-TRV130 treatment failed to produce tolerance to antinociception or GI inhibition, and abuse-related effects were enhanced by repeated treatment. Effects of acute and repeated (+)-TRV130 in these procedures resemble effects of morphine, with the exception that TRV130 antinociception was more resistant to tolerance. (−)-TRV130 was inactive. Conclusions These results suggest that TRV130 retains undesirable constipating and abuse-related effects during repeated treatment despite its bias for G-protein signaling.

Cannabinoid CB 1 receptors (CB 1 Rs) mediate the presynaptic effects of endocannabinoids in the central nervous system (CNS) and most behavioral effects of exogenous cannabinoids. Cannabinoid receptor-interacting protein 1a (CRIP 1a ) binds to the CB 1 R C-terminus and can attenuate constitutive CB 1 R-mediated inhibition of Ca 21 channel activity. We now demonstrate cellular colocalization of CRIP 1a at neuronal elements in the CNS and show that CRIP 1a inhibits both constitutive and agonist-stimulated CB 1 Rmediated guanine nucleotide-binding regulatory protein (G-protein) activity. Stable overexpression of CRIP 1a in human embryonic kidney (HEK)-293 cells stably expressing CB 1 Rs (CB 1 -HEK), or in N18TG2 cells endogenously expressing CB 1 Rs, decreased CB 1 Rmediated G-protein activation (measured by agonist-stimulated [ activation. These effects were not attributable to differences in CB 1 R expression or endocannabinoid tone because CB 1 R levels did not differ between cell lines varying in CRIP 1a expression, and endocannabinoid levels were undetectable (CB 1 -HEK) or unchanged (N18TG2) by CRIP 1a overexpression. In CB 1 -HEK cells, 4-hour pretreatment with cannabinoid agonists downregulated CB 1 Rs and desensitized agonist-stimulated [ 35 S]GTPgS binding. CRIP 1a overexpression attenuated CB 1 R downregulation without altering CB 1 R desensitization. Finally, in cultured autaptic hippocampal neurons, CRIP 1a overexpression attenuated both depolarizationinduced suppression of excitation and inhibition of excitatory synaptic activity induced by exogenous application of cannabinoid but not by adenosine A1 agonists. These results confirm that CRIP 1a inhibits constitutive CB 1 R activity and demonstrate that CRIP 1a can also inhibit agonist-stimulated CB 1 R signaling and downregulation of CB 1 Rs. Thus, CRIP 1a appears to act as a broad negative regulator of CB 1 R function.

The 6β-N-heterocyclic naltrexamine derivative, NAP, has been demonstrated to be a peripherally selective mu opioid receptor modulator. To further improve peripheral selectivity of this highly potent ligand, its pyridal ring was quaterinized with benzyl bromide to produce BNAP. In radioligand binding assay, the Ki of BNAP for MOR was 0.76 ± 0.09 nM and was >900 fold more selective for MOR than DOR. The Ki for KOR was 3.46 ± 0.05 nM. In [35S]GTPγS ligand stimulated assay, BNAP showed low agonist efficacy with 14.6% of the maximum response of DAMGO with an EC50 of 4.84 ± 0.6 nM. However, unlike its parent compound NAP, BNAP displayed partial agonist activity at KOR with % maximum response at 45.9 ± 1.7% of U50,488H. BNAP did not reverse morphine-induced antinociception when administered subcutaneously but did antagonize when administered intracerebroventricularly. BNAP antagonized morphine-induced contractions of the circular muscle in mice colon. BNAP inhibition of field-stimulated contractions in longitudinal muscle strips for the guinea-pig ileum were also blocked by nor-BNI, a kappa opioid receptor antagonist. BNAP induced inhibition of acetic acid induced abdominal stretching in chronic morphine treated mice. These findings suggest that BNAP is a dual MOR antagonist/KOR agonist and may have functional use in irritable bowel patients.

Repeated Δ9-tetrahydrocannabinol (THC) administration produces cannabinoid type 1 receptor (CB1R) desensitization and downregulation, as well as tolerance to its in vivo pharmacological effects. However, the magnitude of CB1R desensitization varies by brain region, with CB1Rs in the striatum and its output nuclei undergoing less desensitization than other regions. A growing body of data indicates that regional differences in CB1R desensitization are produced, in part, by THC-mediated induction of the stable transcription factor, ΔFosB, and subsequent regulation of CB1Rs. The purpose of the present study was to determine whether THC-mediated induction of ΔFosB in the striatum inhibits CB1R desensitization in the striatum and output nuclei. This hypothesis was tested using bitransgenic mice with inducible expression of ΔFosB or ΔcJun, a dominant negative inhibitor of AP-1-mediated transcription, in specific forebrain regions. Mice were treated repeatedly with escalating doses of THC or vehicle for 6.5 days, and CB1R-mediated G-protein activation was assessed using CP55,940-stimulated [35S]GTPγS autoradiography. Overexpression of ΔFosB in striatal dopamine type 1 receptor-containing (D1R) medium spiny neurons (MSNs) attenuated CB1R desensitization in the substantia nigra, ventral tegmental area (VTA) and amygdala. Expression of ΔcJun in striatal D1R- and dopamine type 2 receptor (D2R)-containing MSNs enhanced CB1R desensitization in the caudate-putamen and attenuated desensitization in the hippocampus and VTA. THC-mediated in vivo pharmacological effects were then assessed in ΔcJun-expressing mice. Tolerance to THC-mediated hypomotility was enhanced in ΔcJun-expressing mice. These data reveal that ΔFosB and possibly other AP-1 binding proteins regulate CB1R signaling and adaptation in the striatum and limbic system.

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