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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 decreased spontaneous miniature inhibitory postsynaptic currents (mIPSCs) in CeA. (A) Representative CeA mIPSCs before, during the superfusion of 500 nM MT-7716 and washout. (B) Mean ± SEM frequency, amplitude, rise and decay of mIPSCs for CeA neurons from control rats. MT-7716 significantly (* p < 0.001) decreased the mean mIPSC frequencies and amplitude. Statistical significance * was set at p < 0.05 and calculated by Student’s t-test. (C) Cumulative fractions calculated by Kolmogorov-Smirnov sample test show that MT-7716 shifted the cumulative frequency to the right (in 11 out of 12 CeA neurons studied), indicating a longer inter-event interval during its application, suggesting decreased GABA release. (D) Cumulative fractions calculated by Kolmogorov-Smirnov sample test show that MT-7716 shifted the cumulative frequency to the right (in 10 out of 12 CeA neurons studied). MT-7716 shifted the cumulative amplitude to the left, indicating smaller mIPSC amplitudes, suggesting postsynaptic site of action.
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Figure 5: MT-7716 decreased spontaneous miniature inhibitory postsynaptic currents (mIPSCs) in CeA. (A) Representative CeA mIPSCs before, during the superfusion of 500 nM MT-7716 and washout. (B) Mean ± SEM frequency, amplitude, rise and decay of mIPSCs for CeA neurons from control rats. MT-7716 significantly (* p < 0.001) decreased the mean mIPSC frequencies and amplitude. Statistical significance * was set at p < 0.05 and calculated by Student’s t-test. (C) Cumulative fractions calculated by Kolmogorov-Smirnov sample test show that MT-7716 shifted the cumulative frequency to the right (in 11 out of 12 CeA neurons studied), indicating a longer inter-event interval during its application, suggesting decreased GABA release. (D) Cumulative fractions calculated by Kolmogorov-Smirnov sample test show that MT-7716 shifted the cumulative frequency to the right (in 10 out of 12 CeA neurons studied). MT-7716 shifted the cumulative amplitude to the left, indicating smaller mIPSC amplitudes, suggesting postsynaptic site of action.

Mentions: To further characterize the decreased GABA release induced by MT-7716, we examined spontaneous mIPSCs using whole-cell recordings in the presence of 1 μM TTX to eliminate action potential-dependent release of neurotransmitter. Here we tested MT-7716 at 500 nM, a maximal effective and reversible concentration, and found that MT-7716 significantly (p < 0.05) decreased mIPSC frequency to 78.9 ± 5.3% of control (means: control, 0.82 ± 0.3 Hz; MT-7716, 0.67 ± 0.3 Hz; n = 12) with recovery during washout (0.75 ± 0.4 Hz) (Figures 5A, D). MT-7716 significantly decreased the frequency of mIPSCs and shifted the cumulative frequency distribution to longer inter-event intervals (Figures 5A–C), indicating decreased presynaptic GABA release. MT-7716 also significantly (p < 0.05) decreased the amplitude to 90.15 ± 0.5% of control (means: control, 62.3 ± 2.7 pA; MT-7716, 56.06 ± 2.4 pA; n = 12; Figures 5A, B and D), but not the decay or rise time of mIPSCs.


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 decreased spontaneous miniature inhibitory postsynaptic currents (mIPSCs) in CeA. (A) Representative CeA mIPSCs before, during the superfusion of 500 nM MT-7716 and washout. (B) Mean ± SEM frequency, amplitude, rise and decay of mIPSCs for CeA neurons from control rats. MT-7716 significantly (* p < 0.001) decreased the mean mIPSC frequencies and amplitude. Statistical significance * was set at p < 0.05 and calculated by Student’s t-test. (C) Cumulative fractions calculated by Kolmogorov-Smirnov sample test show that MT-7716 shifted the cumulative frequency to the right (in 11 out of 12 CeA neurons studied), indicating a longer inter-event interval during its application, suggesting decreased GABA release. (D) Cumulative fractions calculated by Kolmogorov-Smirnov sample test show that MT-7716 shifted the cumulative frequency to the right (in 10 out of 12 CeA neurons studied). MT-7716 shifted the cumulative amplitude to the left, indicating smaller mIPSC amplitudes, suggesting postsynaptic site of action.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3927450&req=5

Figure 5: MT-7716 decreased spontaneous miniature inhibitory postsynaptic currents (mIPSCs) in CeA. (A) Representative CeA mIPSCs before, during the superfusion of 500 nM MT-7716 and washout. (B) Mean ± SEM frequency, amplitude, rise and decay of mIPSCs for CeA neurons from control rats. MT-7716 significantly (* p < 0.001) decreased the mean mIPSC frequencies and amplitude. Statistical significance * was set at p < 0.05 and calculated by Student’s t-test. (C) Cumulative fractions calculated by Kolmogorov-Smirnov sample test show that MT-7716 shifted the cumulative frequency to the right (in 11 out of 12 CeA neurons studied), indicating a longer inter-event interval during its application, suggesting decreased GABA release. (D) Cumulative fractions calculated by Kolmogorov-Smirnov sample test show that MT-7716 shifted the cumulative frequency to the right (in 10 out of 12 CeA neurons studied). MT-7716 shifted the cumulative amplitude to the left, indicating smaller mIPSC amplitudes, suggesting postsynaptic site of action.
Mentions: To further characterize the decreased GABA release induced by MT-7716, we examined spontaneous mIPSCs using whole-cell recordings in the presence of 1 μM TTX to eliminate action potential-dependent release of neurotransmitter. Here we tested MT-7716 at 500 nM, a maximal effective and reversible concentration, and found that MT-7716 significantly (p < 0.05) decreased mIPSC frequency to 78.9 ± 5.3% of control (means: control, 0.82 ± 0.3 Hz; MT-7716, 0.67 ± 0.3 Hz; n = 12) with recovery during washout (0.75 ± 0.4 Hz) (Figures 5A, D). MT-7716 significantly decreased the frequency of mIPSCs and shifted the cumulative frequency distribution to longer inter-event intervals (Figures 5A–C), indicating decreased presynaptic GABA release. MT-7716 also significantly (p < 0.05) decreased the amplitude to 90.15 ± 0.5% of control (means: control, 62.3 ± 2.7 pA; MT-7716, 56.06 ± 2.4 pA; n = 12; Figures 5A, B and D), but not the decay or rise time of mIPSCs.

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