title: Arginine vasopressin produces inhibition upon respiration without pressor effect in the rat.
abstract: The purpose of the current study was to examine where arginine vasopressin (AVP) inhibits respiration by direct action on the areas of the ventrolateral medulla (VLM) in the rat. The animal was anesthetized by urethane (1.2 g/kg, i.p.), paralyzed with gallamine triethiodide, and artificially ventilated. Catheterization of the femoral artery and vein, and bilateral vagotomy were performed. The rat was then placed upon a stereotaxic instrument in a prone position. The phrenic nerve was separated and cut peripherally. Phrenic nerve activity (PNA) was monitored at normocapnia and hypercapnia in hyperoxia. Microinjection of AVP into various subregions of the VLM was then performed. In response to AVP microinjection, a transient period of apnea and then a significant decrease in PNA amplitude were observed. Arterial blood pressure was unchanged. This inhibition of PNA with AVP treatment was site-specific, attenuated by raising CO2 concentration, and totally abolished by pretreatment with AVP V1A receptor antagonist. Data of the present study indicate that endogenous resource of AVP may produce an inhibitory effect upon respiration via AVP receptors presented on neurons within the VLM.
authors.affiliation: Department of Biology, National Taiwan Normal University, Taipei, Taiwan, ROC.
authors.forename: Ching-Wen
authors.initials: CW
authors.lastname: Chuang
authors.forename: Meng-Tzu
authors.initials: MT
authors.lastname: Cheng
authors.forename: Jin-Tun
authors.initials: JT
authors.lastname: Lin
authors.forename: Hsin-Yun
authors.initials: HY
authors.lastname: Hsien
authors.forename: Hzi-Yu
authors.initials: HY
authors.lastname: Hung
authors.forename: Ji-Chuu
authors.initials: JC
authors.lastname: Hwang
mesh_terms: D000818:Animals; D065092:Antidiuretic Hormone Receptor Antagonists; D001049:Apnea / Q000139:chemically induced; D001127:Arginine Vasopressin / Q000008:administration & dosage*; D001794:Blood Pressure / Q000187:drug effects*; D002245:Carbon Dioxide; D005260:Female; D018698:Glutamic Acid / Q000008:administration & dosage; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology; D008845:Microinjections; D010791:Phrenic Nerve / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D017483:Receptors, Vasopressin / Q000502:physiology; D012119:Respiration / Q000187:drug effects*; D015656:Respiratory Mechanics / Q000187:drug effects
chemical_list: D065092:Antidiuretic Hormone Receptor Antagonists; D017483:Receptors, Vasopressin; D001127:Arginine Vasopressin; D002245:Carbon Dioxide; D018698:Glutamic Acid