title: Adenosine increases total venous capacitance in awake instrumented rats.
abstract: To determine the effect of adenosine on the venous system, mean circulatory filling pressure (MCFP) was determined during infusion of intravenous (i.v.) adenosine (66.5 to a maximum of 532 microgram.kg-1.min-1) in 9 awake instrumented rats before and during ganglionic blockade with i.v. hexamethonium, 0.6 mg.kg-1.min-1. MCFP, the equilibrated pressure (mm Hg) occurring when the circulation is arrested by transient inflation of a balloon in the right atrium, is inversely related to total venous capacitance. Both adenosine and hexamethonium caused a reduction in mean arterial pressure (MAP); heart rate (HR) decreased during adenosine infusion in the blocked, but not the unblocked, state. In the unblocked state, baseline MCFP was 6.5 +/- 0.3 mmHg; hexamethonium caused baseline MCFP to decrease to 5.3 +/- 0.3 mm Hg. In both the unblocked and the blocked state, adenosine caused a dose-related decrease in MCFP [6.5 +/- 0.3 to 5.5 +/- 0.6 mm Hg (532 microgram.kg-1.min-1 adenosine dose) unblocked state; and 5.3 +/- 0.3 to 4.3 +/- 0.3 mm Hg (400 microgram.kg-1.min-1 adenosine dose) blocked state]. This decrease in MCFP induced by adenosine was highly significant. Intravenous adenosine, in an awake instrumented rat model, increases venous capacitance, with and without ganglionic blockade.
authors.affiliation: Department of Medicine, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey 17033.
authors.forename: M R
authors.initials: MR
authors.lastname: Glick
authors.forename: J D
authors.initials: JD
authors.lastname: Gehman
authors.forename: J A
authors.initials: JA
authors.lastname: Gascho
mesh_terms: D000109:Acetylcholine / Q000008:administration & dosage / Q000494:pharmacology; D000241:Adenosine / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D006323:Heart Arrest / Q000139:chemically induced; D006339:Heart Rate / Q000187:drug effects*; D018738:Hexamethonium; D006584:Hexamethonium Compounds / Q000008:administration & dosage / Q000494:pharmacology*; D007262:Infusions, Intravenous; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D014680:Veins / Q000187:drug effects* / Q000502:physiology
chemical_list: D006584:Hexamethonium Compounds; D018738:Hexamethonium; D000241:Adenosine; D000109:Acetylcholine