title: Activation of mu-opioid receptors in the ventrolateral orbital cortex inhibits the GABAergic miniature inhibitory postsynaptic currents in rats.
abstract: Previous studies have indicated that mu-opioid receptors in the ventrolateral orbital cortex (VLO) are involved in antinociception in tail flick tests and GABAergic neurons or terminals express mu-opioid receptors in the VLO. The current study examined the effect of selective mu-opioid receptor agonist DAMGO on the GABAergic miniature inhibitory postsynaptic currents (mIPSCs) in the VLO in rats using the whole-cell patch clamp. The results demonstrated that 5 μM DAMGO application into the rat VLO slices significantly reduced the GABAergic mIPSCs frequency, without any effect on its amplitude, and this effect of DAMGO was reversed by pretreatment with selective mu-opioid receptor antagonist 1 μM CTOP. Importantly, application of CTOP alone into the VLO slices did not produce any effect on the frequency and amplitude of GABAergic mIPSCs. These results indicate a presynaptic effect of mu-opioid receptor activation on the GABAergic neurons in the VLO. The current data suggests that a presynaptic inhibition of the GABA release may contribute to the mu-opioid receptor mediated effects in the VLO and provides novel electrophysiological evidence for the underlying mechanisms of mu-opioid receptors in the VLO.
authors.affiliation: Department of Physiology and Pathophysiology, Key Laboratory of Environment and Genes Related to Diseases, Ministry of Education, Xi'an Jiaotong University School of Medicine, Xi'an 710061, China. Electronic address: quchaoling@gmail.com.
authors.forename: Chao-Ling
authors.initials: CL
authors.lastname: Qu
authors.affiliation: Department of Physiology and Pathophysiology, Key Laboratory of Environment and Genes Related to Diseases, Ministry of Education, Xi'an Jiaotong University School of Medicine, Xi'an 710061, China.
authors.forename: Fu-Quan
authors.initials: FQ
authors.lastname: Huo
authors.affiliation: Institute of Neuroscience and Physiology, Göteborg University, Box 433, Göteborg, SE-40530, Sweden.
authors.forename: Fen-Sheng
authors.initials: FS
authors.lastname: Huang
authors.affiliation: Department of Physiology and Pathophysiology, Key Laboratory of Environment and Genes Related to Diseases, Ministry of Education, Xi'an Jiaotong University School of Medicine, Xi'an 710061, China.
authors.forename: Jing-Shi
authors.initials: JS
authors.lastname: Tang
mesh_terms: D000818:Animals; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000494:pharmacology; D066298:In Vitro Techniques; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects*; D055369:Miniature Postsynaptic Potentials / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D017397:Prefrontal Cortex / Q000187:drug effects* / Q000502:physiology; D017207:Rats, Sprague-Dawley; D017450:Receptors, Opioid, mu / Q000819:agonists* / Q000037:antagonists & inhibitors; D013004:Somatostatin / Q000031:analogs & derivatives / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
chemical_list: D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; C049352:phenylalanyl-cyclo(cysteinyltyrosyl-tryptophyl-ornithyl-threonyl-penicillamine)threoninamide; D013004:Somatostatin; D005680:gamma-Aminobutyric Acid
keywords: GABA; Mu-opioid receptor; Rats; Ventrolateral orbital cortex; mIPSCs