title: Cardiovascular and respiratory interactions of hyperosmolar saline, scorpion toxin, and veratridine in rats.
abstract: This study evaluates the cardiovascular and respiratory effects evoked by hypertonic sodium chloride solution (HSS) and the possible interactions of these effects with scorpion toxin (TX) or veratridine (V). Groups 1 (1 mL/kg, rapid), 2 (4 mL/kg, rapid), and 3 (4 mL/kg, slow) were used for comparison of HSS administered by rapid or slow injection. HSS (4 mL/kg) was injected after bilateral vagotomy (group 4) or administration of atropine (group 5). In groups 6 (1 mL/kg in bolus), 7 (4 mL/kg in bolus), and 8 (4 mL/kg/60 s), HSS was injected 20 min after the administration of TX (250 microg/kg). In group 9, two doses of V (25 microg/kg, i.v.) were injected 10 min apart. Concomitantly with the second dose of V, HSS (4 mL/kg) was injected into the jugular vein. HSS administered by rapid injection (1 mL/kg) resulted in hypotension, hyperventilation, and a slight decrease in heart rate. However, when HSS was administered after TX, only bradypnea was observed. HSS (4 mL/kg, rapid) induced a rapid and marked fall in blood pressure, bradycardia, and apnea. However, when HSS was administered after TX, a more pronounced bradycardia and a smaller reduction in mean arterial pressure were observed. Slow injection of HSS (60 s) evoked hypotension, hyperventilation, and bradycardia. The same dose injected after TX resulted in bradypnea and a smaller reduction in blood pressure. The HSS-induced hypotension was attenuated by previous administration of atropine or by vagotomy, whereas bradycardia was prevented by previous injection of atropine, but not by bilateral vagotomy. Like vagotomy, atropinization prevented the apnea and bradypnea produced by HSS (4 mL/kg in bolus). V evoked a slight bradycardia, hypotension, and apnea. These effects were potentiated when V was injected concomitantly with HSS. The effects of HSS are dependent on both volume and speed of injection, and are affected by previous injection of TX or concomitant injection of V.
authors.affiliation: Laboratory of Medical Investigation, Clinical Emergencies, School of Medicine, Universidade de São Paulo, SP, Brazil.
authors.forename: Marcus Vinicius Melo
authors.initials: MV
authors.lastname: Andrade
authors.forename: Irineu Tadeu
authors.initials: IT
authors.lastname: Velasco
authors.forename: Tasso
authors.initials: T
authors.lastname: Moraes-Santos
authors.forename: Júnio Rios
authors.initials: JR
authors.lastname: Melo
authors.forename: Gnana Keith Marques
authors.initials: GK
authors.lastname: de Araújo
authors.forename: José Renan
authors.initials: JR
authors.lastname: Cunha-Meio
mesh_terms: D000818:Animals; D001285:Atropine / Q000008:administration & dosage; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D002319:Cardiovascular System / Q000187:drug effects*; D004347:Drug Interactions; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D051381:Rats; D012119:Respiration / Q000187:drug effects; D012137:Respiratory System / Q000187:drug effects*; D012462:Saline Solution, Hypertonic / Q000008:administration & dosage*; D012604:Scorpion Venoms / Q000008:administration & dosage*; D014628:Vagotomy; D014655:Vascular Resistance / Q000187:drug effects; D014701:Veratridine / Q000008:administration & dosage*
chemical_list: D012462:Saline Solution, Hypertonic; D012604:Scorpion Venoms; D014701:Veratridine; D001285:Atropine