Search

Remifentanil (REM) and fentanyl (FEN) are commonly used analgesics that act by activating a µ-opioid receptor (MOR). Although optimal concentrations of REM can be easily maintained during surgery, it is sometimes switched to FEN for optimal pain regulation. However, standards for this switching protocol remain unclear. Opioid anesthetic efficacy is decided in part by MOR desensitization; thus, in this study, we investigated the desensitization profiles of REM and FEN to MOR. The efficacy and potency during the 1st administration of REM or FEN in activating the MOR were almost equal. Similarly, in β arrestin recruitment, which determines desensitization processes, they showed no significant differences. In contrast, the 2nd administration of FEN resulted in a stronger MOR desensitization potency than that of REM, whereas REM showed a higher internalization potency than FEN. These results suggest that different β arrestin-mediated signaling caused by FEN or REM led to their distinct desensitization and internalization processes. Our three-dimensional analysis, with in silico binding of REM and FEN to MOR models, highlighted that REM and FEN bound to similar but distinct sites of MOR and led to distinct β arrestin-mediated profiles, suggesting that distinct binding profiles to MOR may alter β arrestin activity, which accounts for MOR desensitization and internalization.

Background Oral mucositis (OM) associated with cancer treatment not only impairs patients’ quality of life but also causes treatment delays or changes. This prospective exploratory study was conducted to evaluate the efficacy of Episil® oral liquid, which is an approved protective formulation for the oral mucosa in patients with OM. The extent of the pain-relieving effect, feeling during use, and adverse events or problems were evaluated. Methods In total, 10 Japanese cancer patients with OM receiving chemotherapy, pretreatment therapy for hematopoietic stem cell transplantation, or radiation therapy for head and neck cancer were enrolled. Results A numerical rating scale (NRS) was used to assess oral pain intensity due to OM. Compared to baseline, the mean NRS began to decrease at 5 min after using Episil® (7.1 ± 1.4 to 4.6 ± 2.87; p = 0.264). A significant decrease was observed in the pain score after using Episil® compared with that before using Episil®, and this effect lasted up to 120 min. The protective effects of Episil® were observed 3–5 min after application. Some patients felt slight soreness or discomfort when applying Episil®. However, this discomfort due to Episil®’s stimulation was within the allowable range and transient. No adverse events were observed in any of the cases. Conclusions The results of this prospective study showed that Episil® could be an effective treatment to relieve oral pain in Japanese patients with moderate to severe OM, and this newly approved product might adequately support patients’ oral intake. Trial registration University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR) (UMIN000031921).

Prototypic antidepressants, such as tricyclic/tetracyclic antidepressants (TCAs), have multiple pharmacological properties and have been considered to be more effective than newer antidepressants, such as selective serotonin reuptake inhibitors (SSRIs), in treating severe depression. However, the molecular mechanisms underlying the high efficacy of TCAs have not been completely understood. Herein, we found that lysophosphatidic acid receptor 1 (LPAR1), a G protein-coupled receptor, mediates the antidepressant effects of amitriptyline, a typical TCA. Amitriptyline directly bound to LPAR1 and activated downstream G protein signaling without affecting β-arrestin signaling, which implied that amitriptyline could act as a G protein-biased agonist of LPAR1. This biased agonism is unique to TCAs and has not been observed in other antidepressants, such as SSRIs. Long-term infusion of mouse hippocampus with 1-oleoyl-2-O-methyl-glycerophosphothionate (OMPT), a potent G protein-biased LPAR1 agonist, induced behavior similar to that induced by antidepressants. In contrast, LPA, a non-biased agonist of LPAR1, induced anxious behavior, indicating that LPAR1 may regulate conflicting emotional behaviors because of the downstream signaling bias. Furthermore, RNA-seq analysis revealed that LPA and OMPT have opposite patterns of gene expression changes in hippocampus. Ingenuity pathway analysis indicated that chronic intrahippocampal administration of OMPT could activate LPAR1 downstream signaling (Rho and MAPK), whereas LPA suppressed LPAR1 signaling. The results reveal the unique antidepressant effects of TCAs and indicate the potential of G protein-biased agonists of LPAR1 as targets for novel antidepressants.

Ghrelin is a pleiotropic feeding hormone which also has a pivotal role in the central nervous system. Upon the activation of its receptor, growth hormone secretagogue receptor (GHSR), the Gα q/11 -mediated and the β-arrestin-mediated signaling pathways are activated. As the β-arrestin pathway is a potential drug target, there is a strong need for β-arrestin-biased GHSR modulators. Activation of the β-arrestin pathway should inhibit the Gα q/11 -mediated calcium flux through the internalization of the receptor. Hence, we used the antagonistic activity in the calcium assay as the first screening for the β-arrestin activation. By conducting the second screening assay for the β-arrestin activation based on extracellular signal regulated kinase (ERK) 1/2 phosphorylation, we discovered a putative β-arrestin-biased superagonist. The activity of the compound was not completely blocked with the competitive antagonist, which implies that the effect is mediated, at least partly, by allosteric binding of the compound.

TRV130 (oliceridine), a G protein-biased ligand for μ-opioid receptor, has recently been synthesized. It is considered to have strong antinociceptive effects and only minor adverse effects. However, whether or not oliceridine actually exhibits an ideal pharmacological profile as an analgesic has not yet been fully clarified in animal studies. This study examined the pharmacological profile of oliceridine in cells and animals. Oliceridine (10 μM) did not produce any μ-opioid receptor internalization in cells even though it increased impedance, which reflects the activation of Gi protein using the CellKey™ system, and inhibited the formation of cAMP. In mice, oliceridine (0.3–10 mg/kg) produced a dose-dependent antinociceptive effect with a rapid-onset and short-duration action in the hot-plate test, as well as antihyperalgesia after sciatic nerve ligation without the development of antinociceptive tolerance using the thermal hyperalgesia test. On the other hand, oliceridine inhibited gastrointestinal transit. Furthermore, oliceridine produced rapid-onset hyperlocomotion at antinociceptive doses; sensitization developed in mice and an emetic effect was observed in ferrets. These results indicate that, although oliceridine may produce dopamine-related behaviors even through selective stimulation of the G-protein-biased μ-opioid receptor pathway, it still offers advantages for breakthrough pain without antinociceptive tolerance with adequate doses.

Transdermal fentanyl is widely used in the treatment of severe pain because of convenience, safety, and stable blood concentrations. Nevertheless, patients often develop tolerance to fentanyl, necessitating the use of other opioids; transdermal buprenorphine patch is widely used as an analgesic agent, though available formulation does not provide comparable analgesic effect as transdermal fentanyl patch. Opioids bind to the opioid receptor (OR) to activate both G protein-mediated and β-arrestin-mediated pathways. We synthesized morphine-related compounds with high transdermal absorbability (N1 and N2) and evaluated their OR activities pharmacologically in comparison with fentanyl and morphine.In cells stably expressing μ-opioid receptor (MOR), δ-opioid receptor (DOR), and κ-opioid receptor (KOR), G protein-mediated pathways were assessed using the CellKey and an intracellular cyclic adenosine monophosphate (cAMP) assay, while β-arrestin-mediated pathways were analyzed with β-arrestin recruitment and receptor internalization assays. Furthermore, analgesic effects were evaluated using a tail-flick test in mice, and the analgesic effect on fentanyl-tolerant mice was evaluated.In the CellKey and cAMP assays, both N1 and N2 showed the highest affinity for MOR and acted as full agonists as well as partial agonists for DOR and KOR. In the β-arrestin and internalization assays, only fentanyl acted as a full agonist; N1 and N2 acted as partial agonists of MOR. In the mouse tail-flick test, N1 and N2 showed analgesic effects equivalent to those of fentanyl and morphine. In fentanyl-tolerant mice, fentanyl showed a diminished analgesic effect, whereas N1 and N2 as well as morphine retained their analgesic effects.While N1 and N2 have higher transdermal absorbability than fentanyl, they also have analgesic effects comparable to those of morphine, suggesting that they may be attractive compounds for the development of novel opioid patches for transitioning from fentanyl patches.

It has been considered that activation of peripheral μ-opioid receptors (MORs) induces side effects of opioids. In this study, we investigated the possible improvement of the immune system in tumour-bearing mice by systemic administration of the peripheral MOR antagonist naldemedine.The inhibitory effect of naldemedine on MOR-mediated signalling was tested by cAMP inhibition and β-arrestin recruitment assays using cultured cells. We assessed possible changes in tumour progression and the number of splenic lymphocytes in tumour-bearing mice under the repeated oral administration of naldemedine.Treatment with naldemedine produced a dose-dependent inhibition of both the decrease in the cAMP level and the increase in β-arrestin recruitment induced by the MOR agonists. Repeated treatment with naldemedine at a dose that reversed the morphine-induced inhibition of gastrointestinal transport, but not antinociception, significantly decreased tumour volume and prolonged survival in tumour-transplanted mice. Naldemedine administration significantly decreased the increased expression of immune checkpoint-related genes and recovered the decreased level of toll-like receptor 4 in splenic lymphocytes in tumour-bearing mice.The blockade of peripheral MOR may induce an anti-tumour effect through the recovery of T-cell exhaustion and promotion of the tumour-killing system.

Positive allosteric modulators (PAMs) of G protein-coupled receptors (GPCRs) have drawn attention as novel drug candidates. PAMs can enhance the activities of endogenous agonists which are not only secreted at appropriate times and in parts of the body, but also are immediately metabolized. Therefore, they are expected to show fewer side effects than exogeneous orthosteric ligands. Recently, we have reported that oxytocin (OT) functioned as a PAM of the μ opioid receptor (MOR) which was one of the most potent targets for analgesics. OT is thus thought to be a useful compound for the development of novel analgesics. In this study, several OT analogs were synthesized and evaluated with an intact cell-based assay to investigate the crucial structures of OT for exerting the PAM activity. The assay results indicated that the cyclic structure formed by an intramolecular disulfide bond and the three C-terminal residues containing a small Gly residue of OT were essential for their function as a MOR-PAM. Intriguingly, two analogs having an amide or an ethylene tether instead of the intramolecular disulfide bridge did not have any PAM effects. The results suggested that the disulfide linkage of OT would be a key structure for exerting the PAM activity at the MOR.

Activated opioid receptors transmit internal signals through two major pathways: the G-protein-mediated pathway, which exerts analgesia, and the β-arrestin-mediated pathway, which leads to unfavorable side effects. Hence, G-protein-biased opioid agonists are preferable as opioid analgesics. Rubiscolins, the spinach-derived naturally occurring opioid peptides, are selective δ opioid receptor agonists, and their p.o. administration exhibits antinociceptive effects. Although the potency and effect of rubiscolins as G-protein-biased molecules are partially confirmed, their in vitro profiles remain unclear. We, therefore, evaluated the properties of rubiscolins, in detail, through several analyses, including the CellKeyTM assay, cADDis® cAMP assay, and PathHunter® β-arrestin recruitment assay, using cells stably expressing µ, δ, κ, or µ/δ heteromer opioid receptors. In the CellKeyTM assay, rubiscolins showed selective agonistic effects for δ opioid receptor and little agonistic or antagonistic effects for µ and κ opioid receptors. Furthermore, rubiscolins were found to be G-protein-biased δ opioid receptor agonists based on the results obtained in cADDis® cAMP and PathHunter® β-arrestin recruitment assays. Finally, we found, for the first time, that they are also partially agonistic for the µ/δ dimers. In conclusion, rubiscolins could serve as attractive seeds, as δ opioid receptor-specific agonists, for the development of novel opioid analgesics with reduced side effects.

Chemotherapy often induces oral ulcerative mucositis (OUM) in patients with cancer, characterized by severe painful inflammation. Mouth-washing with the Japanese herbal medicine hangeshashinto (HST) ameliorates chemotherapy-induced OUM in patients with colorectal cancer. Previously, we demonstrated that HST decreased interleukin 1β-induced prostaglandin E2 production in human oral keratinocytes (HOKs) and OUM-induced mechanical or spontaneous pain in rats. However, HST effects on tissue repair functions in HOKs remain unclear. Here, we examined the effects of HST on scratch-induced wound healing in vitro and in vivo. In vitro, HST enhanced wound healing mainly through scratch-induced HOK migration. Screening of the seven constituent medicinal herbs and their major components revealed that Scutellaria root, processed ginger, and Glycyrrhiza components mainly induced the scratch-induced HOK migration. Pharmacokinetic analyses indicated that the active ingredient concentrations in rat plasma following oral HST administration were below the effective doses for HOK migration, suggesting direct effects of HST in OUM. Mitogen-activated protein kinase and C-X-C chemokine receptor 4 inhibitors significantly suppressed HST-induced HOK migration. Moreover, HST enhanced tissue repair in our OUM rat model. Thus, HST likely enhanced OUM tissue repair through oral keratinocyte migration upon MAPK and CXCR4 activation and may be useful in patients with cancer-associated OUM.

Although the advantages of sp3 -rich, sterically complicated molecules in drug development have been pointed out, modern screening libraries are filled with planar, sp2 -rich components. Compounds that are sp3 -rich are difficult to synthesize, and thus we aimed to invent an efficient method to construct sp3 -rich libraries. By modifying sp3 -rich 7-azanorbornane scaffolds through click chemistry, we efficiently prepared a small set of compounds. These compounds were not only sp3 -rich, but also had sufficient "lead-like" properties in view of molecular weights and hydrophobicity. Screening assays of this library provided weak κ opioid receptor agonists and growth hormone secretagogue receptor agonists with high hit rates. These results indicate that the 7-azanorbornane scaffold may be a "privileged structure" for lead identification in drug discovery.

Morphine, fentanyl, and oxycodone are widely used as analgesics, and recently hydromorphone has been approved in Japan. Although all of these are selective for μ-opioid receptors (MORs) and have similar structures, their analgesic potencies and adverse effects (AEs) are diverse. Recent molecular analyses of MOR signaling revealed that the G protein-mediated signaling pathway causes analgesic effects and the β-arrestin-mediated signaling pathway is responsible for AEs. We used several cell-based analyses that selectively measure cellular responses activated by either G protein- or β-arrestin-mediated pathways. GloSensor™ cAMP, CellKey™, and receptor internalization assays were performed with four different types of cells stably expressing differentially labelled MOR. EC50 values measured by cAMP and CellKey™ assays had potencies in the order fentanyl ≤ hydromorphone

Oral mucositis (OM) is one of the most frequently observed adverse oral events in radiation therapy for patients with head and neck cancer. Thus, objective evaluation of OM severity is needed for early and timely intervention. Here, we analyzed the time-course of salivary metabolomic profiles during the radiation therapy. The severity of OM (National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events v3.0) of nine patients with head and neck cancer was evaluated. Partial least squares regression-discriminant analysis, using samples collected before radiation therapy, showed that histidine and tyrosine highly discriminated high-grade OM from low-grade OM before the start of radiation therapy (significant difference, p = 0.048 for both metabolites). Further, the pretreatment concentrations of gamma-aminobutyric acid and 2-aminobutyric acids were higher in the high-grade OM group. Although further validations are still necessary, this study showed potentially associated metabolites with worse radiotherapy-related OM among patients with head and neck cancer.

Several clinical studies have reported that Japanese herbal medicine Hangeshashinto (HST) has beneficial effects on chemotherapy-induced oral ulcerative mucositis (OUM). Our previous research demonstrated that HST improves chemotherapy-induced OUM through human oral keratinocyte (HOK) migration, which was suppressed by mitogen-activated protein kinase (MAPK) and C-X-C chemokine receptor 4 (CXCR4) inhibitors. However, the association between these molecules and HOK migration was unclear. Here, we examined the effects of HST on the expression of CXCR4/CXCR7 and C-X-C motif chemokine ligands 11 and 12 (CXCL11/CXCL12) in HOKs. Our results indicated that HST upregulated CXCL12, but not CXCR4, CXCR7, nor CXCL11 in HOKs. HST-induced expression of CXCL12 was significantly suppressed by an inhibitor of extracellular signal-regulated kinase (ERK), but not of p38 and c-Jun N-terminal kinase (JNK). In addition, HST induced phosphorylation of ERK in HOKs. These findings suggest that HST enhances HOK migration by upregulating CXCL12 via ERK.

Background The misuse of opioids has led to an epidemic in recent times. The endothelin A receptor (ETAR) has recently attracted attention as a novel therapeutic target to enhance opioid analgesia. We hypothesized that endothelin A receptors may affect pain mechanisms by heterodimerization with μ opioid receptors. We examined the mechanisms of ETAR-mediated pain and the potential therapeutic effects of an ETAR antagonist, Compound-E, as an agent for analgesia. Methods Real-time in vitro effect of Compound-E on morphine response was assessed in HEK293 cells expressing both endothelin A and μ opioid receptors through CellKey™ and cADDis cAMP assays. Endothelin A/μ opioid receptor dimerization was assessed by immunoprecipitation and live cell imaging. The in vivo effect of Compound-E was evaluated using a morphine analgesia mouse model that observed escape response behavior, body temperature, and locomotor activity. Results In CellKey™ and cAMP assays, pretreatment of cells with endothelin-1 attenuated morphine-induced responses. These responses were improved by Compound-E, but not by BQ-123 nor by bosentan, an ETAR and endothelin B receptor antagonist. Dimerization of ETARs and μ opioid receptors was confirmed by Western blot and total internal reflection fluorescence microscopy in live cells. In vivo, Compound-E potentiated and prolonged the analgesic effects of morphine, enhanced hypothermia, and increased locomotor activity compared to morphine alone. Conclusion The results suggest that attenuation by endothelin-1 of morphine analgesia may be caused by dimerization of Endothelin A/μ opioid receptors. The novel ETAR antagonist Compound-E could be an effective adjunct to reduce opioid use.

Opioid agonists elicit their analgesic action mainly via μ opioid receptors; however, their use is limited because of adverse events including constipation and respiratory depression. It has been shown that analgesic action is transduced by the G protein-mediated pathway whereas adverse events are by the β-arrestin-mediated pathway through μ opioid receptor signaling. The first new-generation opioid TRV130, which preferentially activates G protein- but not β-arrestin-mediated signal, was constructed and developed to reduce adverse events. TRV130 and other G protein-biased compounds tend to elicit desirable analgesic action with less adverse effects. In clinical trials, the intravenous TRV130 (oliceridine) was evaluated in Phase I, II and III clinical studies. Here we review the discovery and synthesis of TRV130, its main action as a novel analgesic having less adverse events, its up-to-date status in clinical trials, and additional concerns about TRV130 as demonstrated in the literature.

Cancer cachexia is highly prevalent in gastric cancer patients and characterized by decreased food consumption and body weight. We previously created a rat model of cancer cachexia using MKN45cl85 and 85As2 cells derived from human gastric cancer. The 85As2 cells induced cachexia more potently compared to MKN45cl85 cells. To clarify the mechanism underlying the difference in the cachexia-inducing ability of these cells, we conducted DNA microarray analysis, focusing on cell proliferation and the production of leukemia inhibitory factor (LIF), a cachexia-inducing factor. The plasma human LIF levels of 85As2-induced cachexic rats increased as symptoms worsened, whereas the plasma levels of MKNcl85 were low. 85As2 cells displayed more genetic changes compared to MKN45cl85 cells, which were related to Toll-like receptor (TLR) 4/5 signaling. Stimulation of both cells with TLR4 (lipopolysaccharide) or TLR5 (flagellin) agonists did not affect proliferation. However, in 82As2 cells, LIF production was significantly increased by stimulation with TLR5, which was suppressed by an inhibitor of interleukin-1 receptor-associated kinase-1/4, which are important factors in the TLR5 signaling pathway. The increase in LIF production resulting from activation of the TLR5 signaling pathway may contribute to the cachexia-inducing ability of 85As2 cells.

Neuropathic pain resulting from peripheral neuronal damage is largely resistant to treatment with currently available analgesic drugs. Recently, ATP, lysophosphatidic acid, and platelet-activating factor (PAF) have been reported to play important inductive roles in neuropathic pain. In the present study, we found that pain-like behaviors resulting from partial sciatic nerve ligation (PSL) were largely attenuated by deficiency of lysophosphatidylcholine acyltransferase (LPCAT)2, which is one of the PAF biosynthetic enzymes. By contrast, deficiency of the other PAF biosynthetic enzyme, LPCAT1, did not ameliorate neuropathic pain. With regard to the mechanism of the observed effects, LPCAT2 was detected in wild-type spinal cord microglia, and the absence of LPCAT2 expression precluded spinal PAF expression in LPCAT2-knockout mice. Furthermore, ATP-stimulated PAF biosynthesis in macrophages was decreased by pretreatment with the PAF receptor antagonist ABT-491, indicating the existence of a positive feedback loop of PAF biosynthesis, which we designated the PAF-pain loop. In conclusion, LPCAT2 is a novel therapeutic target for newly categorized analgesic drugs; in addition, our data call for the re-evaluation of the clinical utility of PAF receptor antagonists.-Shindou, H., Shiraishi, S., Tokuoka, S. M., Takahashi Y., Harayama, T., Abe, T., Bando, K., Miyano, K., Kita, Y., Uezono, Y., Shimizu, T. Relief from neuropathic pain by blocking of the platelet-activating factor-pain loop.

Chemotherapy often induces oral ulcerative mucositis (OUM) in patients with cancer, characterized by severe painful inflammation. Mouth-washing with the Japanese herbal medicine hangeshashinto (HST) ameliorates chemotherapy-induced OUM in patients with colorectal cancer. Previously, we demonstrated that HST decreased interleukin 1β-induced prostaglandin E2 production in human oral keratinocytes (HOKs) and OUM-induced mechanical or spontaneous pain in rats. However, HST effects on tissue repair functions in HOKs remain unclear. Here, we examined the effects of HST on scratch-induced wound healing in vitro and in vivo. In vitro, HST enhanced wound healing mainly through scratch-induced HOK migration. Screening of the seven constituent medicinal herbs and their major components revealed that Scutellaria root, processed ginger, and Glycyrrhiza components mainly induced the scratch-induced HOK migration. Pharmacokinetic analyses indicated that the active ingredient concentrations in rat plasma following oral HST administration were below the effective doses for HOK migration, suggesting direct effects of HST in OUM. Mitogen-activated protein kinase and C-X-C chemokine receptor 4 inhibitors significantly suppressed HST-induced HOK migration. Moreover, HST enhanced tissue repair in our OUM rat model. Thus, HST likely enhanced OUM tissue repair through oral keratinocyte migration upon MAPK and CXCR4 activation and may be useful in patients with cancer-associated OUM.

Although the advantages of sp

Cancer was considered an incurable disease for many years; however, with the development of anticancer drugs and state-of-the art technologies, it has become curable. Cardiovascular diseases in patients with cancer or induced by cancer chemotherapy have recently become a great concern. Certain anticancer drugs and molecular targeted therapies cause cardiotoxicity, which limit the widespread implementation of cancer treatment and decrease the quality of life in cancer patients significantly. The anthracycline doxorubicin (DOX) causes cardiotoxicity. The cellular mechanism underlying DOX-induced cardiotoxicity include free-radical damage to cardiac myocytes, leading to mitochondrial injury and subsequent death of myocytes. Recently, circulating orexigenic hormones, ghrelin and des-acyl ghrelin, have been reported to inhibit DOX-induced cardiotoxicity. However, little is known about the molecular mechanisms underlying their preventive effects. In the present study, we show the possible mechanisms underlying the effects of ghrelin and des-acyl ghrelin against DOX-induced cardiotoxicity through in vitro and in vivo researches.

Preclinical and clinical evidence suggests that glial cell line-derived neurotrophic factor (GDNF) is important in the therapeutic effect of antidepressants. A previous study demonstrated that the tricyclic antidepressant amitriptyline induces Gαi/o activation, which leads to GDNF expression in astrocytes. However, the specific target expressed in astrocytes that mediates antidepressant-evoked Gαi/o activation has yet to be identified. Thus, the current study explored the possibility that antidepressant-induced Gαi/o activation depends on lysophosphatidic acid receptor 1 (LPAR1), a Gαi/o-coupled receptor. GDNF mRNA expression was examined using real-time PCR and Gαi/o activation was examined using the cell-based receptor assay system CellKeyTM in rat C6 astroglial cells and rat primary cultured astrocytes. LPAR1 antagonists blocked GDNF mRNA expression and Gαi/o activation evoked by various classes of antidepressants (amitriptyline, nortriptyline, mianserin, and fluoxetine). In addition, deletion of LPAR1 by RNAi suppressed amitriptyline-evoked GDNF mRNA expression. Treatment of astroglial cells with the endogenous LPAR agonist LPA increased GDNF mRNA expression through LPAR1, whereas treatment of primary cultured neurons with LPA failed to affect GDNF mRNA expression. Astrocytic GDNF expression evoked by either amitriptyline or LPA utilized, in part, transactivation of fibroblast growth factor receptor and a subsequent ERK cascade. The current results suggest that LPAR1 is a novel, specific target of antidepressants that leads to GDNF expression in astrocytes.

The growth hormone secretagogue receptor (GHS-R) belongs to Gαq-coupled G protein-coupled receptor (GPCR) that mediates growth hormone release, food intake, appetite, glucose metabolism and body composition. Ghrelin has been identified as an endogenous ligand for GHS-R, and it is the only orexigenic peptide found in the peripheral organs. Olanzapine, an atypical antipsychotic agent that binds to and inhibits the activation of GPCR for several neurotransmitters, has metabolic side effects such as excessive appetite and weight gain. Recently, studies have revealed that the orexigenic mechanism of olanzapine is mediated via GHS-R signaling, although the precise mechanisms have not been clarified. In this study, we investigated the effect of olanzapine on ghrelin-mediated GHS-R signaling by using an electrical impedance-based receptor biosensor assay system (CellKey™). Olanzapine at concentrations of 10(-7) and 10(-6)mol/L enhanced ghrelin-induced (10(-10)-10(-8)mol/L) GHS-R activation. A Ca(2+) imaging assay revealed that olanzapine (10(-7) and 10(-6)mol/L) enhanced ghrelin (10(-7) M)-induced GHS-R activity. In contrast, haloperidol (an antipsychotic agent) failed to enhance this ghrelin-mediated GHS-R activation, as demonstrated by both the CellKey™ and Ca(2+) imaging assays. Together, these results suggest that olanzapine, but not haloperidol, promotes appetite by enhancing ghrelin-mediated GHS-R signaling.