Regulation of arterial blood pressure in the common green iguana.
Arterial blood pressure (ABP) responses to graded hemorrhage and passive head-up tilt were studied in restrained, anesthetized, and unanesthetized iguanas. The ABP fell slowly in response to hemorrhage up to a critical deficit of 35 plus or minus 19% of the estimated blood volume; the rate of ABP fall then increased nearly 40-fold to continued hemorrhage. Increased heart rate and decreased femoral arterial blood flow accompanied progressive hemorrhage. Propranolol (2-3 mug/kg) did not appreciably alter arterial pressure-hemorrhage curves but hemorrhage-induced increases in heart rate were diminished nearly 50%. Atropine had little effect on either the blood pressure or heart rate changes induced by hemorrhage. During passive tilts of 0-90 degrees carotid arterial pressure fell 33% before returning to control levels (2 min). Heart rate increased and femoral arterial blood flow and central venous pressure fell in response to head-up tilts. It is concluded that hemorrhage and passive head-up tilting can induce reflex cardiovascular changes that assist ABP regulation in iguanas.
D000758:Anesthesia; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D001810:Blood Volume; D002339:Carotid Arteries / Q000502:physiology; D002496:Central Venous Pressure; D005263:Femoral Artery / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects; D006470:Hemorrhage / Q000503:physiopathology; D008116:Lizards / Q000502:physiology*; D011433:Propranolol / Q000494:pharmacology; D012018:Reflex; D012039:Regional Blood Flow; D013312:Stress, Physiological
D001285:Atropine; D011433:Propranolol