title: Nicotine excites corticotropin-releasing hormone mRNA-expressing neuron in the hypothalamic paraventricular nucleus in vitro in rats.
abstract: Nicotine is known to modulate the activity of the hypothalamic-pituitary-adrenal axis by stimulating corticotropin-releasing hormone (CRH) release from the hypothalamic paraventricular nucleus (PVN). However, the mechanism by which nicotine affects the hypothalamic-pituitary-adrenal axis by modulating PVN CRH neuronal activity is currently unclear. Here, we examined the effects of nicotine on PVN CRH-mRNA-expressing neurons in vitro in rats by whole-cell patch-clamp recordings, biocytin staining, and single-cell reverse transcription-multiplex PCR techniques. Of the 146 PVN putative parvocellular neurons, 17.1% (25/146) coexpressed GAPDH mRNA and CRH mRNA. Under current-clamp recording conditions, application of nicotine (1 μM) induced excitation in 92% (23/25) PVN CRH-mRNA-expressing neurons, which showed a significant increase in the spike firing rate accompanied by a depolarization of the membrane potential. Nicotine induced an increase in the spike firing rate of PVN CRH-mRNA-expressing neurons in a concentration-dependent manner. The half-effective concentration (EC50) of nicotine for increasing the spike firing rate of PVN CRH-mRNA-expressing neurons was 1.6 μM. Extracellular application of ionotropic glutamate receptor antagonist kynurenic acid (1 mM) abolished the nicotine-induced excitation of PVN CRH-mRNA-expressing neurons. Moreover, application of nicotine induced a significant increase in the spontaneous excitatory postsynaptic currents frequency, but without significantly altering the spontaneous excitatory postsynaptic currents amplitude of the CRH-mRNA-expressing neurons. Biocytin staining confirmed that the nicotine-sensitive CRH-mRNA-expressing neurons were located in the PVN parvocellular division. These results indicated that extracellular administration of nicotine indirectly excited PVN CRH-mRNA-expressing neurons, suggesting that nicotine modulated PVN CRH secretion by enhancement of both the presynaptic action potential drive and quantal glutamate release.
authors.affiliation: aDepartment of Osteology, Affiliated Hospital of Yanbian University bCellular Function Research Center cDepartment of Physiology and Pathophysiology, College of Medicine, Yanbian University, Yanji City, Jilin Province, China.
authors.forename: Bai-Ri
authors.initials: BR
authors.lastname: Cui
authors.forename: Bin-Bin
authors.initials: BB
authors.lastname: Zhang
authors.forename: Chun-Ping
authors.initials: CP
authors.lastname: Chu
authors.forename: Xun
authors.initials: X
authors.lastname: Cui
authors.forename: De-Lai
authors.initials: DL
authors.lastname: Qiu
mesh_terms: D000818:Animals; D003346:Corticotropin-Releasing Hormone / Q000187:drug effects* / Q000378:metabolism*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects*; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects; D008239:Lysine / Q000031:analogs & derivatives; D008297:Male; D060885:Multiplex Polymerase Chain Reaction; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009538:Nicotine / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D010913:Pituitary-Adrenal System / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013194:Staining and Labeling
chemical_list: D018722:Nicotinic Agonists; D012333:RNA, Messenger; D009538:Nicotine; D003346:Corticotropin-Releasing Hormone; C013411:biocytin; D008239:Lysine