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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 decreases evoked GABAergic transmission in CeA neurons. (A)Left panel: Representative recordings of evoked IPSPs in CeA neurons from naïve rats recorded before, during, and after washout from application of MT-7716 at all the concentrations tested. (B)Right Panel: Histograms representing the percent of the peak decrease in evoked (at half max stimulus intensity) IPSP amplitudes during superfusion of different concentrations (100, 250, 500, and 1000 nM) of MT-7716 and washout. Overall ANOVA revealed that MT-7716 decreased statistically significantly the IPSP amplitudes. Post hoc Newman-Keuls showed significant effect for all the doses at half max stimulus intensity. (*) Indicates p < 0.01.
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Figure 1: MT-7716 decreases evoked GABAergic transmission in CeA neurons. (A)Left panel: Representative recordings of evoked IPSPs in CeA neurons from naïve rats recorded before, during, and after washout from application of MT-7716 at all the concentrations tested. (B)Right Panel: Histograms representing the percent of the peak decrease in evoked (at half max stimulus intensity) IPSP amplitudes during superfusion of different concentrations (100, 250, 500, and 1000 nM) of MT-7716 and washout. Overall ANOVA revealed that MT-7716 decreased statistically significantly the IPSP amplitudes. Post hoc Newman-Keuls showed significant effect for all the doses at half max stimulus intensity. (*) Indicates p < 0.01.

Mentions: We recorded from 81 CeA neurons from male Wistar rats. The mean RMP was −78 ± 1.7 mV and the mean input resistance was 115 ± 5 M. We evoked pharmacologically isolated GABAA-IPSPs by stimulating locally within the CeA and IPSP input-output (I/O) curves were generated. Based on our previous electrophysiological data on N/OFQ (Roberto and Siggins, 2006) we generated a dose-response curve testing four ranged concentrations (100 nM, 250 nM 500 nM and 1 μM) of MT-7716 on the mean amplitude of evoked IPSPs in CeA neurons from naïve-control rats (Figures 1A, B). We applied MT-7716 on CeA slices for 15–20 min and washed out for more than 25 min, until partial or complete recovery was obtained. In Figure 1B, we expressed the data as percent of control using the middle stimulus intensity obtained from the I-O relationship. The graphs in Figures 2A–D plot the percentage effect of MT-7716 on the IPSP amplitude for the three stimulus intensities and the washout.


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 decreases evoked GABAergic transmission in CeA neurons. (A)Left panel: Representative recordings of evoked IPSPs in CeA neurons from naïve rats recorded before, during, and after washout from application of MT-7716 at all the concentrations tested. (B)Right Panel: Histograms representing the percent of the peak decrease in evoked (at half max stimulus intensity) IPSP amplitudes during superfusion of different concentrations (100, 250, 500, and 1000 nM) of MT-7716 and washout. Overall ANOVA revealed that MT-7716 decreased statistically significantly the IPSP amplitudes. Post hoc Newman-Keuls showed significant effect for all the doses at half max stimulus intensity. (*) Indicates p < 0.01.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: MT-7716 decreases evoked GABAergic transmission in CeA neurons. (A)Left panel: Representative recordings of evoked IPSPs in CeA neurons from naïve rats recorded before, during, and after washout from application of MT-7716 at all the concentrations tested. (B)Right Panel: Histograms representing the percent of the peak decrease in evoked (at half max stimulus intensity) IPSP amplitudes during superfusion of different concentrations (100, 250, 500, and 1000 nM) of MT-7716 and washout. Overall ANOVA revealed that MT-7716 decreased statistically significantly the IPSP amplitudes. Post hoc Newman-Keuls showed significant effect for all the doses at half max stimulus intensity. (*) Indicates p < 0.01.
Mentions: We recorded from 81 CeA neurons from male Wistar rats. The mean RMP was −78 ± 1.7 mV and the mean input resistance was 115 ± 5 M. We evoked pharmacologically isolated GABAA-IPSPs by stimulating locally within the CeA and IPSP input-output (I/O) curves were generated. Based on our previous electrophysiological data on N/OFQ (Roberto and Siggins, 2006) we generated a dose-response curve testing four ranged concentrations (100 nM, 250 nM 500 nM and 1 μM) of MT-7716 on the mean amplitude of evoked IPSPs in CeA neurons from naïve-control rats (Figures 1A, B). We applied MT-7716 on CeA slices for 15–20 min and washed out for more than 25 min, until partial or complete recovery was obtained. In Figure 1B, we expressed the data as percent of control using the middle stimulus intensity obtained from the I-O relationship. The graphs in Figures 2A–D plot the percentage effect of MT-7716 on the IPSP amplitude for the three stimulus intensities and the washout.

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