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Chuang CW, Chang KP, Cho HY, Chuang TH, Yu MC, Wu CL, Wu SN. Characterization of Inhibitory Capability on Hyperpolarization-Activated Cation Current Caused by Lutein (β,ε-Carotene-3,3'-Diol), a Dietary Xanthophyll Carotenoid. Int J Mol Sci 2022; 23:7186. [PMID: 35806190 PMCID: PMC9266545 DOI: 10.3390/ijms23137186] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 06/24/2022] [Accepted: 06/25/2022] [Indexed: 02/07/2023] Open
Abstract
Lutein (β,ε-carotene-3,3'-diol), a xanthophyll carotenoid, is found in high concentrations in the macula of the human retina. It has been recognized to exert potential effectiveness in antioxidative and anti-inflammatory properties. However, whether and how its modifications on varying types of plasmalemmal ionic currents occur in electrically excitable cells remain incompletely answered. The current hypothesis is that lutein produces any direct adjustments on ionic currents (e.g., hyperpolarization-activated cation current, Ih [or funny current, If]). In the present study, GH3-cell exposure to lutein resulted in a time-, state- and concentration-dependent reduction in Ih amplitude with an IC50 value of 4.1 μM. There was a hyperpolarizing shift along the voltage axis in the steady-state activation curve of Ih in the presence of this compound, despite being void of changes in the gating charge of the curve. Under continued exposure to lutein (3 μM), further addition of oxaliplatin (10 μM) or ivabradine (3 μM) could be effective at either reversing or further decreasing lutein-induced suppression of hyperpolarization-evoked Ih, respectively. The voltage-dependent anti-clockwise hysteresis of Ih responding to long-lasting inverted isosceles-triangular ramp concentration-dependently became diminished by adding this compound. However, the addition of 10 μM lutein caused a mild but significant suppression in the amplitude of erg-mediated or A-type K+ currents. Under current-clamp potential recordings, the sag potential evoked by long-lasting hyperpolarizing current stimulus was reduced under cell exposure to lutein. Altogether, findings from the current observations enabled us to reflect that during cell exposure to lutein used at pharmacologically achievable concentrations, lutein-perturbed inhibition of Ih would be an ionic mechanism underlying its changes in membrane excitability.
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Affiliation(s)
- Chao-Wei Chuang
- Department of Ophthalmology, Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chiayi City 60002, Taiwan; (C.-W.C.); (K.-P.C.)
| | - Kuo-Pin Chang
- Department of Ophthalmology, Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chiayi City 60002, Taiwan; (C.-W.C.); (K.-P.C.)
| | - Hsin-Yen Cho
- Department of Physiology, National Cheng Kung University Medical College, Tainan 70101, Taiwan; (H.-Y.C.); (T.-H.C.); (M.-C.Y.)
| | - Tzu-Hsien Chuang
- Department of Physiology, National Cheng Kung University Medical College, Tainan 70101, Taiwan; (H.-Y.C.); (T.-H.C.); (M.-C.Y.)
| | - Meng-Cheng Yu
- Department of Physiology, National Cheng Kung University Medical College, Tainan 70101, Taiwan; (H.-Y.C.); (T.-H.C.); (M.-C.Y.)
| | - Chao-Liang Wu
- Department of Medical Research, Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chiayi 60002, Taiwan;
| | - Sheng-Nan Wu
- Department of Physiology, National Cheng Kung University Medical College, Tainan 70101, Taiwan; (H.-Y.C.); (T.-H.C.); (M.-C.Y.)
- Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan 70101, Taiwan
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Inhibitory Effectiveness in Delayed-Rectifier Potassium Current Caused by Vortioxetine, Known to Be a Novel Antidepressant. Biomedicines 2022; 10:biomedicines10061318. [PMID: 35740340 PMCID: PMC9220334 DOI: 10.3390/biomedicines10061318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 05/25/2022] [Accepted: 06/01/2022] [Indexed: 01/27/2023] Open
Abstract
Vortioxetine (VOR) is recognized to exert antidepressant actions. However, whether this drug modifies ionic currents in excitable cells remains unclear. The aim of this study was to explore the electrophysiological effects of VOR and other related compounds in pituitary GH3 cells and in Neuro-2a cells. VOR suppressed the delayed-rectifier K+ current (IK(DR)) in a concentration-, time-, and state-dependent manner. Effective IC50 values needed to inhibit peak and sustained IK(DR) were computed to be 31.2 and 8.5 μM, respectively, while the KD value estimated from minimal binding scheme was 7.9 μM. Cell exposure to serotonin (10 μM) alone failed to alter IK(DR), while fluoxetine (10 μM), a compound structurally similar to VOR, mildly suppressed current amplitude. In continued presence of VOR, neither further addition of propranolol nor risperidone reversed VOR-mediated inhibition of IK(DR). Increasing VOR concentration not only depressed IK(DR) conductance but also shifted toward the hyperpolarized potential. As the VOR concentration was raised, the recovery of IK(DR) block became slowed. The IK(DR) activated by a downsloping ramp was suppressed by its presence. The inhibition of IK(DR) by a train pulse was enhanced during exposure to VOR. In Neuro-2a cells, this drug decreased IK(DR). Overall, inhibitory effects of VOR on ionic currents might constitute another underlying mechanism of its actions.
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Cho HY, Chen PC, Chuang TH, Yu MC, Wu SN. Activation of Voltage-Gated Na+ Current by GV-58, a Known Activator of CaV Channels. Biomedicines 2022; 10:biomedicines10030721. [PMID: 35327523 PMCID: PMC8945347 DOI: 10.3390/biomedicines10030721] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 03/10/2022] [Accepted: 03/17/2022] [Indexed: 02/04/2023] Open
Abstract
GV-58 ((2R)-2-[(6-{[(5-methylthiophen-2-yl)methyl]amino}-9-propyl-9H-purin-2-yl)amino]butan-1-ol) is recognized to be an activator of N- and P/Q-type Ca2+ currents. However, its modulatory actions on other types of ionic currents in electrically excitable cells remain largely unanswered. This study was undertaken to explore the possible modifications caused by GV-58 in ionic currents (e.g., voltage-gated Na+ current [INa], A-type K+ current [IK(A)], and erg-mediated K+ current [IK(erg)]) identified from pituitary GH3 lactotrophs. GH3 cell exposure to GV-58 enhanced the transient and late components of INa with varying potencies; consequently, the EC50 values of GV-58 required for its differential increase in peak and late INa in GH3 cells were estimated to be 8.9 and 2.6 μM, respectively. The INa in response to brief depolarizing pulse was respectively stimulated or suppressed by GV-58 or tetrodotoxin, but it failed to be altered by ω-conotoxin MVIID. Cell exposure to this compound increased the recovery of INa inactivation evoked by two-pulse protocol based on a geometrics progression; however, in its presence, there was a slowing in the inactivation rate of current decay evoked by a train of depolarizing pulses. The existence of GV-58 also resulted in an increase in the amplitude of ramp-induced resurgent and window INa. The presence of this compound inhibited IK(A) magnitude, accompanied by a shortening in inactivation time course of the current; however, it mildly decreased IK(erg). Under current-clamp conditions, GV-58 increased the frequency of spontaneous action potentials in GH3 cells. Moreover, in NSC-34 motor neuron-like cells, the presence of GV-58 not only raised INa amplitude but also reduced current inactivation. Taken together, the overall work provides a noticeable yet unidentified finding which implies that, in addition to its agonistic effect on Ca2+ currents, GV-58 may concertedly modify the amplitude and gating kinetics of INa in electrically excitable cells, hence modifiying functional activities in these cells.
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Affiliation(s)
- Hsin-Yen Cho
- Department of Physiology, National Cheng Kung University Medical College, Tainan City 70101, Taiwan; (H.-Y.C.); (P.-C.C.); (T.-H.C.); (M.-C.Y.)
| | - Pei-Chun Chen
- Department of Physiology, National Cheng Kung University Medical College, Tainan City 70101, Taiwan; (H.-Y.C.); (P.-C.C.); (T.-H.C.); (M.-C.Y.)
- Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan City 70101, Taiwan
| | - Tzu-Hsien Chuang
- Department of Physiology, National Cheng Kung University Medical College, Tainan City 70101, Taiwan; (H.-Y.C.); (P.-C.C.); (T.-H.C.); (M.-C.Y.)
| | - Meng-Cheng Yu
- Department of Physiology, National Cheng Kung University Medical College, Tainan City 70101, Taiwan; (H.-Y.C.); (P.-C.C.); (T.-H.C.); (M.-C.Y.)
| | - Sheng-Nan Wu
- Department of Physiology, National Cheng Kung University Medical College, Tainan City 70101, Taiwan; (H.-Y.C.); (P.-C.C.); (T.-H.C.); (M.-C.Y.)
- Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan City 70101, Taiwan
- Correspondence: ; Tel.: +886-6-2353535-5334; Fax: +886-6-2362780
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Evidence for Inhibitory Perturbations on the Amplitude, Gating, and Hysteresis of A-Type Potassium Current, Produced by Lacosamide, a Functionalized Amino Acid with Anticonvulsant Properties. Int J Mol Sci 2022; 23:ijms23031171. [PMID: 35163091 PMCID: PMC8835568 DOI: 10.3390/ijms23031171] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 01/11/2022] [Accepted: 01/19/2022] [Indexed: 02/05/2023] Open
Abstract
Lacosamide (Vimpat®, LCS) is widely known as a functionalized amino acid with promising anti-convulsant properties; however, adverse events during its use have gradually appeared. Despite its inhibitory effect on voltage-gated Na+ current (INa), the modifications on varying types of ionic currents caused by this drug remain largely unexplored. In pituitary tumor (GH3) cells, we found that the presence of LCS concentration-dependently decreased the amplitude of A-type K+ current (IK(A)) elicited in response to membrane depolarization. The IK(A) amplitude in these cells was sensitive to attenuation by the application of 4-aminopyridine, 4-aminopyridine-3-methanol, or capsaicin but not by that of tetraethylammonium chloride. The effective IC50 value required for its reduction in peak or sustained IK(A) was calculated to be 102 or 42 µM, respectively, while the value of the dissociation constant (KD) estimated from the slow component in IK(A) inactivation at varying LCS concentrations was 52 µM. By use of two-step voltage protocol, the presence of this drug resulted in a rightward shift in the steady-state inactivation curve of IK(A) as well as in a slowing in the recovery time course of the current block; however, no change in the gating charge of the inactivation curve was detected in its presence. Moreover, the LCS addition led to an attenuation in the degree of voltage-dependent hysteresis for IK(A) elicitation by long-duration triangular ramp voltage commands. Likewise, the IK(A) identified in mouse mHippoE-14 neurons was also sensitive to block by LCS, coincident with an elevation in the current inactivation rate. Collectively, apart from its canonical action on INa inhibition, LCS was effective at altering the amplitude, gating, and hysteresis of IK(A) in excitable cells. The modulatory actions on IK(A), caused by LCS, could interfere with the functional activities of electrically excitable cells (e.g., pituitary tumor cells or hippocampal neurons).
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Fletcher PA, Sherman A, Stojilkovic SS. Common and diverse elements of ion channels and receptors underlying electrical activity in endocrine pituitary cells. Mol Cell Endocrinol 2018; 463:23-36. [PMID: 28652171 PMCID: PMC5742314 DOI: 10.1016/j.mce.2017.06.022] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 06/20/2017] [Accepted: 06/22/2017] [Indexed: 12/30/2022]
Abstract
The pituitary gland contains six types of endocrine cells defined by hormones they secrete: corticotrophs, melanotrophs, gonadotrophs, thyrotrophs, somatotrophs, and lactotrophs. All these cell types are electrically excitable, and voltage-gated calcium influx is the major trigger for their hormone secretion. Along with hormone intracellular content, G-protein-coupled receptor and ion channel expression can also be considered as defining cell type identity. While many aspects of the developmental and activity dependent regulation of hormone and G-protein-coupled receptor expression have been elucidated, much less is known about the regulation of the ion channels needed for excitation-secretion coupling in these cells. We compare the spontaneous and receptor-controlled patterns of electrical signaling among endocrine pituitary cell types, including insights gained from mathematical modeling. We argue that a common set of ionic currents unites these cells, while differential expression of another subset of ionic currents could underlie cell type-specific patterns. We demonstrate these ideas using a generic mathematical model, showing that it reproduces many observed features of pituitary electrical signaling. Mapping these observations to the developmental lineage suggests possible modes of regulation that may give rise to mature pituitary cell types.
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Affiliation(s)
- Patrick A Fletcher
- Laboratory of Biological Modeling, National Institute of Diabetes, Digestive and Kidney Diseases, NIH, Bethesda, MD, USA.
| | - Arthur Sherman
- Laboratory of Biological Modeling, National Institute of Diabetes, Digestive and Kidney Diseases, NIH, Bethesda, MD, USA
| | - Stanko S Stojilkovic
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD, USA
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Han XF, Zhu YL, Hernandez M, Keating DJ, Chen C. Ghrelin reduces voltage-gated potassium currents in GH3 cells via cyclic GMP pathways. Endocrine 2005; 28:217-24. [PMID: 16388096 DOI: 10.1385/endo:28:2:217] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2005] [Revised: 06/05/2005] [Accepted: 06/10/2005] [Indexed: 11/11/2022]
Abstract
Ghrelin is an endogenous growth hormone secretagogue (GHS) causing release of GH from pituitary somatotropes through the GHS receptor. Secretion of GH is linked directly to intracellular free Ca(2+) concentration ([Ca(2+)]i), which is determined by Ca(2+) influx and release from intracellular Ca(2+) storage sites. Ca(2+) influx is via voltage-gated Ca(2+) channels, which are activated by cell depolarization. Membrane potential is mainly determined by transmembrane K(+) channels. The present study investigates the in vitroeffect of ghrelin on membrane voltage-gated K(+) channels in the GH3 rat somatotrope cell line. Nystatin-perforated patch clamp recording was used to record K(+) currents under voltage-clamp conditions. In the presence of Co(2+) (1 mM, Ca(2+) channel blocker) and tetrodotoxin (1 microM, Na(+) channel blocker) in the bath solution, two types of voltage-gated K(+) currents were characterized on the basis of their biophysical kinetics and pharmacological properties. We observed that transient K(+) current (IA) represented a significant proportion of total K(+) currents in some cells, whereas delayed rectifier K(+) current (IK) existed in all cells. The application of ghrelin (10 nM) reversibly and significantly decreased the amplitude of both IA and IK currents to 48% and 64% of control, respectively. Application of apamin (1 microM, SK channel blocker) or charybdotoxin (1 microM, BK channel blocker) did not alter the K(+) current or the response to ghrelin. The ghrelin-induced reduction in K(+) currents was not affected by PKC and PKA inhibitors. KT5823, a specific PKG inhibitor, totally abolished the K+ current response to ghrelin. These results suggest that ghrelin-induced reduction of voltage-gated K(+) currents in GH3 cells is mediated through a PKG-dependent pathway. A decrease in voltage-gated K(+) currents may increase the frequency, duration, and amplitude of action potentials and contribute to GH secretion from somatotropes.
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Affiliation(s)
- Xue Feng Han
- Department of Physiology, Fourth Military Medical University, Shannxi, China
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Secondo A, Pannaccione A, Cataldi M, Sirabella R, Formisano L, Di Renzo G, Annunziato L. Nitric oxide induces [Ca2+]i oscillations in pituitary GH3 cells: involvement of IDR and ERG K+ currents. Am J Physiol Cell Physiol 2005; 290:C233-43. [PMID: 16207796 DOI: 10.1152/ajpcell.00231.2005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The role of nitric oxide (NO) in the occurrence of intracellular Ca2+ concentration ([Ca2+]i) oscillations in pituitary GH3 cells was evaluated by studying the effect of increasing or decreasing endogenous NO synthesis with L-arginine and nitro-L-arginine methyl ester (L-NAME), respectively. When NO synthesis was blocked with L-NAME (1 mM) [Ca2+]i, oscillations disappeared in 68% of spontaneously active cells, whereas 41% of the quiescent cells showed [Ca2+]i oscillations in response to the NO synthase (NOS) substrate L-arginine (10 mM). This effect was reproduced by the NO donors NOC-18 and S-nitroso-N-acetylpenicillamine (SNAP). NOC-18 was ineffective in the presence of the L-type voltage-dependent Ca2+ channels (VDCC) blocker nimodipine (1 microM) or in Ca2+-free medium. Conversely, its effect was preserved when Ca2+ release from intracellular Ca2+ stores was inhibited either with the ryanodine-receptor blocker ryanodine (500 microM) or with the inositol 1,4,5-trisphosphate receptor blocker xestospongin C (3 microM). These results suggest that NO induces the appearance of [Ca2+]i oscillations by determining Ca2+ influx. Patch-clamp experiments excluded that NO acted directly on VDCC but suggested that NO determined membrane depolarization because of the inhibition of voltage-gated K+ channels. NOC-18 and SNAP caused a decrease in the amplitude of slow-inactivating (IDR) and ether-à-go-go-related gene (ERG) hyperpolarization-evoked, deactivating K+ currents. Similar results were obtained when GH3 cells were treated with L-arginine. The present study suggests that in GH3 cells, endogenous NO plays a permissive role for the occurrence of spontaneous [Ca2+]i oscillations through an inhibitory effect on IDR and on IERG.
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Affiliation(s)
- Agnese Secondo
- Division of Pharmacology, Dept. of Neuroscience, School of Medicine, Federico II Univ. of Naples, via Sergio Pansini 5, 80131 Naples, Italy
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Piros ET, Charles RC, Song L, Evans CJ, Hales TG. Cloned delta-opioid receptors in GH(3) cells inhibit spontaneous Ca(2+) oscillations and prolactin release through K(IR) channel activation. J Neurophysiol 2000; 83:2691-8. [PMID: 10805669 DOI: 10.1152/jn.2000.83.5.2691] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Opioid receptors can couple to K(+) and Ca(2+) channels, adenylyl cyclase, and phosphatidyl inositol turnover. Any of these actions may be important in the regulation of neurotransmitter and hormone release from excitable cells. GH(3) cells exhibit spontaneous oscillations of intracellular Ca(2+) concentration ([Ca(2+)](i)) and prolactin release. Activation of cloned delta-opioid receptors stably expressed in GH(3) cells inhibits both spontaneous Ca(2+) signaling and basal prolactin release. The objective of this study was to examine a possible role for K(+) channels in these processes using the patch-clamp technique, fluorescence imaging, and a sensitive ELISA for prolactin. The selective delta receptor agonist [D-Pen(2), D-Pen(2)]enkephalin (DPDPE) inhibited [Ca(2+)](i) oscillations in GH(3) cells expressing both mu and delta receptors (GH(3)MORDOR cells) but had no effect on control GH(3) cells or cells expressing mu receptors alone (GH(3)MOR cells). The inhibition of [Ca(2+)](i) oscillations by DPDPE was unaffected by thapsigargin pretreatment, suggesting that this effect is independent of inositol 1,4,5-triphosphate-sensitive Ca(2+) stores. DPDPE caused a concentration-dependent inhibition of prolactin release from GH(3)MORDOR cells with an IC(50) of 4 nM. DPDPE increased inward K(+) current recorded from GH(3)MORDOR cells but had no significant effect on K(+) currents recorded from control GH(3) cells or GH(3)MOR cells. The mu receptor agonist morphine also had no effect on currents recorded from control cells but activated inward K(+) currents recorded from GH(3)MOR and GH(3)MORDOR cells. Somatostatin activated inward currents recorded from all three cell lines. The DPDPE-sensitive K(+) current was inwardly rectifying and was inhibited by Ba(2+) but not TEA. DPDPE had no effect on delayed rectifier-, Ca(2+)-, and voltage-activated or A-type K(+) currents, recorded from GH(3)MORDOR cells. Ba(2+) attenuated the inhibition of [Ca(2+)](i) and prolactin release by DPDPE, whereas TEA had no effect, consistent with an involvement of K(IR) channels in these actions of the opioid.
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MESH Headings
- Adenylate Cyclase Toxin
- Adenylyl Cyclases/metabolism
- Analgesics, Opioid/pharmacology
- Animals
- Barium/pharmacology
- Biological Clocks/physiology
- Calcium/metabolism
- Calcium Channels/drug effects
- Calcium Channels/metabolism
- Cell Line
- Cesium/pharmacology
- Enkephalin, D-Penicillamine (2,5)-/antagonists & inhibitors
- Enkephalin, D-Penicillamine (2,5)-/pharmacology
- Enzyme-Linked Immunosorbent Assay
- Naloxone/pharmacology
- Narcotic Antagonists/pharmacology
- Patch-Clamp Techniques
- Potassium/metabolism
- Potassium Channel Blockers
- Potassium Channels/metabolism
- Prolactin/analysis
- Prolactin/metabolism
- Quaternary Ammonium Compounds/pharmacology
- Rats
- Receptors, Opioid, delta/antagonists & inhibitors
- Receptors, Opioid, delta/genetics
- Receptors, Opioid, delta/metabolism
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/antagonists & inhibitors
- Virulence Factors, Bordetella/pharmacology
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Affiliation(s)
- E T Piros
- Department of Physiology, Cornell University, New York, NY 10021, USA
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