Control of glutamate and GABA release by nociceptin/orphanin FQ in the rat lateral amygdala.
The actions of the heptadecapeptide termed nociceptin or orphanin FQ (N/OFQ) and the recently discovered putative precursor product nocistatin were examined on synaptic transmission in putative projection cells of the rat lateral amygdala using the whole-cell patch-clamp technique. N/OFQ decreased evoked non-NMDA receptor-mediated excitatory postsynaptic current (EPSC) amplitudes in a concentration-dependent manner, with a half-maximal inhibitory effect elicited by 21.8 +/- 7.5 nM and a Hill coefficient of 0.8 +/- 0.2 (n = 22). Responses were maximally suppressed to 70.3 +/- 1.7 % of the control value. The effect of N/OFQ was prevented by 1 microM [Phe1[psi](CH2-NH)Gly2]NC(1-13)NH2 (Phe[psi]N/OFQ), a substance known as an antagonist/partial agonist of the ORL receptor. GABA(A) receptor-mediated inhibitory postsynaptic currents (IPSCs) elicited through intra-amygdaloid stimulation were reduced to 48.0 +/- 6.8 % by 1 microM N/OFQ (n = 5). Nocistatin had no measurable effect on evoked synaptic currents or membrane properties of recorded neurons. N/OFQ reduced the frequency of spontaneous miniature EPSCs and IPSCs to 74.0 +/- 2.6 % and 84.4 +/- 1.1 %, respectively, without affecting the amplitudes. The present findings indicate that N/OFQ, but not nocistatin, inhibits the release of glutamate and GABA in the lateral amygdala, presumably by acting on presynaptic release sites. These mechanisms may add to the role of N/OFQ in reducing stress vulnerability as recently proposed on the basis of behavioural and genetic approaches.
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Institut für Physiologie, Otto-von-Guericke-Universität, D-39120 Magdeburg, Germany.
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D000679:Amygdala / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D005239:Fear / Q000502:physiology; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism*; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018847:Opioid Peptides / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D051381:Rats; D020318:Rats, Long-Evans; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*; D000097629:Nociceptin
D000701:Analgesics, Opioid; D018698:Glutamic Acid; D018847:Opioid Peptides; D014665:Vasodilator Agents; D005680:gamma-Aminobutyric Acid; D000097629:Nociceptin; C111148:nocistatin