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MT-7716, a novel selective nonpeptidergic NOP receptor agonist, effectively blocks ethanol-induced increase in GABAergic transmission in the rat central amygdala.

Kallupi M, Oleata CS, Luu G, Teshima K, Ciccocioppo R, Roberto M - Front Integr Neurosci (2014)

Bottom Line: We found that MT-7716 dose-dependently (100-1000 nM) diminished evoked GABAA receptor-mediated inhibitory postsynaptic potentials (IPSPs) and increased paired-pulse facilitation (PPF) ratio of these evoked IPSPs, suggesting a presynaptic site of action of the MT-7716 by decreasing GABA release at CeA synapses.The presynaptic action of MT-7716 was also supported by the significant decrease in the frequency of miniature inhibitory postsynaptic currents (mIPSCs) induced by the nociceptin receptor (NOP) agonist.A putative selective NOP antagonist, [Nphe1]Nociceptin(1-13)NH2, totally prevented the MT-7716-induced inhibition of IPSP amplitudes indicating that MT-7716 exerts its effect through NOPs.

View Article: PubMed Central - PubMed

Affiliation: Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, La Jolla CA, USA ; Pharmacology Unit, School of Pharmacy, University of Camerino Camerino, Italy.

ABSTRACT
The GABAergic system in the central amygdala (CeA) plays a major role in ethanol dependence and the anxiogenic-like response to ethanol withdrawal. A large body of evidence shows that Nociceptin/Orphanin FQ (N/OFQ) regulates ethanol intake and anxiety-like behavior. In the rat, ethanol significantly augments CeA GABA release, whereas N/OFQ diminishes it. Using electrophysiological techniques in an in vitro slice preparation, in this study we investigated the effects of a nonpeptidergic NOP receptor agonist, MT-7716 [(R)-2-3-[1-(Acenaphthen-1-yl)piperidin-4-yl]-2-oxo-2,3-dihydro-1H-benzimidazol-1-yl-N-methylacetamide hydrochloride hydrate], and its interaction with ethanol on GABAergic transmission in CeA slices of naïve rats. We found that MT-7716 dose-dependently (100-1000 nM) diminished evoked GABAA receptor-mediated inhibitory postsynaptic potentials (IPSPs) and increased paired-pulse facilitation (PPF) ratio of these evoked IPSPs, suggesting a presynaptic site of action of the MT-7716 by decreasing GABA release at CeA synapses. The presynaptic action of MT-7716 was also supported by the significant decrease in the frequency of miniature inhibitory postsynaptic currents (mIPSCs) induced by the nociceptin receptor (NOP) agonist. Interestingly, MT-7716 prevented the ethanol-induced augmentation of evoked IPSPs. A putative selective NOP antagonist, [Nphe1]Nociceptin(1-13)NH2, totally prevented the MT-7716-induced inhibition of IPSP amplitudes indicating that MT-7716 exerts its effect through NOPs. These data provide support for an interaction between the nociceptin and GABAergic systems in the CeA and for the anti-alcohol properties of the NOP activation. The development of a synthetic nonpeptidergic NOP receptor agonist such as MT-7716 may represent a useful therapeutic target for alcoholism.

No MeSH data available.


Related in: MedlinePlus

MT-7716 has no effect on voltage-current relationships on the CeA neurons. (A–D) I/V curves showing that MT-7716, in all doses superfused (100–1000 nM) Overall ANOVA indicates that MT-7716 does not modify the RMP of the CeA neurons (n = 6–11). (A) The mean RMPs for the neurons tested with 100 nM MT-7716 was −81 ± 1.2 mV and was −80 ± 0.5 mV for those tested 250 nM MT-7716 (B). Similarly the RMPs of the 10 and 6 CeA neurons tested with 500 nM and 1000 nM MT-7716 was −81.5 ± 0.9 mV (C) and −81 ± 1.2 mV (D). (E) Representative current clamp recordings of a CeA neuron (RMP = 80 mV; input resistance 113 M) during control and 500 nM MT-7716 superfusion (F). Overall, MT-7716 did not significantly affect the firing pattern or number of action potentials in our CeA neuronal population.
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Figure 4: MT-7716 has no effect on voltage-current relationships on the CeA neurons. (A–D) I/V curves showing that MT-7716, in all doses superfused (100–1000 nM) Overall ANOVA indicates that MT-7716 does not modify the RMP of the CeA neurons (n = 6–11). (A) The mean RMPs for the neurons tested with 100 nM MT-7716 was −81 ± 1.2 mV and was −80 ± 0.5 mV for those tested 250 nM MT-7716 (B). Similarly the RMPs of the 10 and 6 CeA neurons tested with 500 nM and 1000 nM MT-7716 was −81.5 ± 0.9 mV (C) and −81 ± 1.2 mV (D). (E) Representative current clamp recordings of a CeA neuron (RMP = 80 mV; input resistance 113 M) during control and 500 nM MT-7716 superfusion (F). Overall, MT-7716 did not significantly affect the firing pattern or number of action potentials in our CeA neuronal population.

Mentions: We also evaluated if different concentrations of MT-7716 would affect the passive membrane properties of CeA neurons of male Wistar rats. Similar to our N/OFQ studies in Sprague Dawley rats (Roberto and Siggins, 2006), we found that none of the concentrations of MT-7716 used, altered the resting membrane properties (Figures 4A–D). Current–voltage (I–V) relationship analysis showed that MT-7716 at the four concentrations tested had no significant effect on (RMP), conductance (Figures 4A–D), or the number of action potentials upon depolarization across the CeA neurons (Figures 4E, F). The mean of the RMPs and input resistance of the four groups of CeA neurons tested in the dose-dependent study was 80.7 ± 1.5 mV and 117 ± 7.6 MΩ, respectively. Specifically, the number of actions potentials for neurons in response to 200 and 400 pA current injections were: 3.2 ± 1.4 and 9.7 ± 1.8 during control and 3.1 ± 1.5 and 9.2 ± 1.8 during 100 nM MT-7716; 4.6 ± 1.1 and 11.8 ± 1.1 during control and 4.5 ± 1.1 and 12.2 ± 1.4 during 250 nM MT-7716; 4.1 ± 0.9 and 10.9 ± 1.7 during control and 4.3 ± 1.6 and 11.3 ± 2.1 during 500 nM MT-7716; 2.5 ± 1.5 and 8.3 ± 2.4 during control and 2.5 ± 1.6 and 8.3 ± 2.8 during 1000 nM MT-7716. Representative current clamp recordings from a CeA neuron during control conditions (Figure 4E) and application of 500 nM MT-7716 (Figure 4F) are illustrated in Figure 4.


MT-7716, a novel selective nonpeptidergic NOP receptor agonist, effectively blocks ethanol-induced increase in GABAergic transmission in the rat central amygdala.

Kallupi M, Oleata CS, Luu G, Teshima K, Ciccocioppo R, Roberto M - Front Integr Neurosci (2014)

MT-7716 has no effect on voltage-current relationships on the CeA neurons. (A–D) I/V curves showing that MT-7716, in all doses superfused (100–1000 nM) Overall ANOVA indicates that MT-7716 does not modify the RMP of the CeA neurons (n = 6–11). (A) The mean RMPs for the neurons tested with 100 nM MT-7716 was −81 ± 1.2 mV and was −80 ± 0.5 mV for those tested 250 nM MT-7716 (B). Similarly the RMPs of the 10 and 6 CeA neurons tested with 500 nM and 1000 nM MT-7716 was −81.5 ± 0.9 mV (C) and −81 ± 1.2 mV (D). (E) Representative current clamp recordings of a CeA neuron (RMP = 80 mV; input resistance 113 M) during control and 500 nM MT-7716 superfusion (F). Overall, MT-7716 did not significantly affect the firing pattern or number of action potentials in our CeA neuronal population.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
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Figure 4: MT-7716 has no effect on voltage-current relationships on the CeA neurons. (A–D) I/V curves showing that MT-7716, in all doses superfused (100–1000 nM) Overall ANOVA indicates that MT-7716 does not modify the RMP of the CeA neurons (n = 6–11). (A) The mean RMPs for the neurons tested with 100 nM MT-7716 was −81 ± 1.2 mV and was −80 ± 0.5 mV for those tested 250 nM MT-7716 (B). Similarly the RMPs of the 10 and 6 CeA neurons tested with 500 nM and 1000 nM MT-7716 was −81.5 ± 0.9 mV (C) and −81 ± 1.2 mV (D). (E) Representative current clamp recordings of a CeA neuron (RMP = 80 mV; input resistance 113 M) during control and 500 nM MT-7716 superfusion (F). Overall, MT-7716 did not significantly affect the firing pattern or number of action potentials in our CeA neuronal population.
Mentions: We also evaluated if different concentrations of MT-7716 would affect the passive membrane properties of CeA neurons of male Wistar rats. Similar to our N/OFQ studies in Sprague Dawley rats (Roberto and Siggins, 2006), we found that none of the concentrations of MT-7716 used, altered the resting membrane properties (Figures 4A–D). Current–voltage (I–V) relationship analysis showed that MT-7716 at the four concentrations tested had no significant effect on (RMP), conductance (Figures 4A–D), or the number of action potentials upon depolarization across the CeA neurons (Figures 4E, F). The mean of the RMPs and input resistance of the four groups of CeA neurons tested in the dose-dependent study was 80.7 ± 1.5 mV and 117 ± 7.6 MΩ, respectively. Specifically, the number of actions potentials for neurons in response to 200 and 400 pA current injections were: 3.2 ± 1.4 and 9.7 ± 1.8 during control and 3.1 ± 1.5 and 9.2 ± 1.8 during 100 nM MT-7716; 4.6 ± 1.1 and 11.8 ± 1.1 during control and 4.5 ± 1.1 and 12.2 ± 1.4 during 250 nM MT-7716; 4.1 ± 0.9 and 10.9 ± 1.7 during control and 4.3 ± 1.6 and 11.3 ± 2.1 during 500 nM MT-7716; 2.5 ± 1.5 and 8.3 ± 2.4 during control and 2.5 ± 1.6 and 8.3 ± 2.8 during 1000 nM MT-7716. Representative current clamp recordings from a CeA neuron during control conditions (Figure 4E) and application of 500 nM MT-7716 (Figure 4F) are illustrated in Figure 4.

Bottom Line: We found that MT-7716 dose-dependently (100-1000 nM) diminished evoked GABAA receptor-mediated inhibitory postsynaptic potentials (IPSPs) and increased paired-pulse facilitation (PPF) ratio of these evoked IPSPs, suggesting a presynaptic site of action of the MT-7716 by decreasing GABA release at CeA synapses.The presynaptic action of MT-7716 was also supported by the significant decrease in the frequency of miniature inhibitory postsynaptic currents (mIPSCs) induced by the nociceptin receptor (NOP) agonist.A putative selective NOP antagonist, [Nphe1]Nociceptin(1-13)NH2, totally prevented the MT-7716-induced inhibition of IPSP amplitudes indicating that MT-7716 exerts its effect through NOPs.

View Article: PubMed Central - PubMed

Affiliation: Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, La Jolla CA, USA ; Pharmacology Unit, School of Pharmacy, University of Camerino Camerino, Italy.

ABSTRACT
The GABAergic system in the central amygdala (CeA) plays a major role in ethanol dependence and the anxiogenic-like response to ethanol withdrawal. A large body of evidence shows that Nociceptin/Orphanin FQ (N/OFQ) regulates ethanol intake and anxiety-like behavior. In the rat, ethanol significantly augments CeA GABA release, whereas N/OFQ diminishes it. Using electrophysiological techniques in an in vitro slice preparation, in this study we investigated the effects of a nonpeptidergic NOP receptor agonist, MT-7716 [(R)-2-3-[1-(Acenaphthen-1-yl)piperidin-4-yl]-2-oxo-2,3-dihydro-1H-benzimidazol-1-yl-N-methylacetamide hydrochloride hydrate], and its interaction with ethanol on GABAergic transmission in CeA slices of naïve rats. We found that MT-7716 dose-dependently (100-1000 nM) diminished evoked GABAA receptor-mediated inhibitory postsynaptic potentials (IPSPs) and increased paired-pulse facilitation (PPF) ratio of these evoked IPSPs, suggesting a presynaptic site of action of the MT-7716 by decreasing GABA release at CeA synapses. The presynaptic action of MT-7716 was also supported by the significant decrease in the frequency of miniature inhibitory postsynaptic currents (mIPSCs) induced by the nociceptin receptor (NOP) agonist. Interestingly, MT-7716 prevented the ethanol-induced augmentation of evoked IPSPs. A putative selective NOP antagonist, [Nphe1]Nociceptin(1-13)NH2, totally prevented the MT-7716-induced inhibition of IPSP amplitudes indicating that MT-7716 exerts its effect through NOPs. These data provide support for an interaction between the nociceptin and GABAergic systems in the CeA and for the anti-alcohol properties of the NOP activation. The development of a synthetic nonpeptidergic NOP receptor agonist such as MT-7716 may represent a useful therapeutic target for alcoholism.

No MeSH data available.


Related in: MedlinePlus