title: Nicotine enhances GABAergic inhibition of oxytocin mRNA-expressing neuron in the hypothalamic paraventricular nucleus in vitro in rats.
abstract: We recently found that extracellular administration of nicotine indirectly excited hypothalamic paraventricular nucleus (PVN) corticotropin-releasing hormone (CRH) mRNA-expressing neurons. In this study, we studied the effect of nicotine on PVN oxytocin (OT) mRNA-expressing neuron in vitro in rats, by whole-cell patch-clamp recording technique, immunohistochemistry methods and single-cell reverse-transcription multiplex polymerase chain reaction (SC-RT-mPCR) methods Our results showed that 79.3% (73/92) of the 92 PVN putative magnocellular neurons co-expressed GAPDH mRNA and OT mRNA. Under current-clamp recording conditions, local micro application of nicotine (1-300μM) induced a decrease in spontaneous firing rate accompanied with a hyperpolarization of membrane potential in 76.7% (56/73) of PVN OT mRNA-expressing magnocellular neurons. The nicotine induced inhibition in spontaneous activity of PVN OT mRNA-expressing magnocellular neurons was dose-dependent. The half-inhibitory concentration (IC50) is 2.9μM. The nicotine induced hyperpolarization of PVN OT mRNA-expressing magnocellular neurons was sensitive to GABAAreceptor antagonist, SR95531 (10μM) and tetrodotoxin (TTX, 1μM). In addition, local micro application of nicotine induced a significant increase in frequency of spontaneous inhibitory postsynaptic potentials (sIPSPs), but without changes in the sEPSPs amplitude of the OT-mRNA expressing neurons. Biocytin staining confirmed that the nicotine-sensitive OT-mRNA expressing neurons were the PVN magnocellular neurons. These results demonstrated that nicotine enhances the GABAergic inhibition, resulting in a decrease in spontaneous firing rate of the PVN OT-mRNA expressing neurons. These findings suggested that nicotine modulated PVN OT secretion via enhancement of both presynaptic action potential drive and quantal GABA release.
authors.affiliation: Key Laboratory of Cellular Function and Pharmacology of Jilin Province, Yanbian University, Yanji City, Jilin Province, 133002, China; Department of Physiology and Pathophysiology, College of Medicine, Yanbian University, Yanji City, Jilin Province, China.
authors.forename: Ke-Min
authors.initials: KM
authors.lastname: Zhang
authors.affiliation: Department of physiology, Jilin Medical College, Jilin City, Jinlin Province, China.
authors.forename: Guo-Yan
authors.initials: GY
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Cellular Function and Pharmacology of Jilin Province, Yanbian University, Yanji City, Jilin Province, 133002, China; Department of Physiology and Pathophysiology, College of Medicine, Yanbian University, Yanji City, Jilin Province, China.
authors.forename: Bin-Bin
authors.initials: BB
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Cellular Function and Pharmacology of Jilin Province, Yanbian University, Yanji City, Jilin Province, 133002, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Xu
authors.affiliation: Key Laboratory of Cellular Function and Pharmacology of Jilin Province, Yanbian University, Yanji City, Jilin Province, 133002, China.
authors.forename: Chun-Ping
authors.initials: CP
authors.lastname: Chu
authors.affiliation: Department of Nephrology, Affiliated Hospital of Yanbian University, Yanji City, Jilin Province, China. Electronic address: kimhua@ybu.edu.cn.
authors.forename: Hua
authors.initials: H
authors.lastname: Jin
authors.affiliation: Key Laboratory of Cellular Function and Pharmacology of Jilin Province, Yanbian University, Yanji City, Jilin Province, 133002, China; Department of Physiology and Pathophysiology, College of Medicine, Yanbian University, Yanji City, Jilin Province, China. Electronic address: dlqiu@ybu.edu.cn.
authors.forename: De-Lai
authors.initials: DL
authors.lastname: Qiu
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D058787:GABA-A Receptor Antagonists / Q000494:pharmacology; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects; D008297:Male; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009538:Nicotine / Q000494:pharmacology*; D010121:Oxytocin / Q000235:genetics / Q000378:metabolism*; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects* / Q000378:metabolism; D011724:Pyridazines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism*; D017208:Rats, Wistar; D013779:Tetrodotoxin / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D058787:GABA-A Receptor Antagonists; D011724:Pyridazines; D012333:RNA, Messenger; D013779:Tetrodotoxin; D010121:Oxytocin; D005680:gamma-Aminobutyric Acid; D009538:Nicotine; C049853:gabazine
keywords: GABA(A) receptor; Nicotine; OT mRNA-expressing neuron; Paraventricular nucleus (PVN); Spontaneous spike firing activity