Effect of magnesium on cocaine-induced, catecholamine-mediated platelet and vascular response in term pregnant ewes.
Ten pregnant ewes were alternated in a study of the blocking effect of parenteral magnesium on the catecholamine response to cocaine. Indirect blood pressures were recorded at 1-minute intervals for 12 minutes before and after a bolus of 2 mg/kg of cocaine. Fetal heart rates were continuously recorded from skin electrodes. Platelet counts were performed before and 12 minutes after cocaine. Control ewes received lactated Ringer's solution, and test animals had 5 mg/kg of elemental magnesium in the form of MgSO4-7H2O in a rapid infusion. A semicrossover was also performed. Platelet counts fell precipitately in controls and rose after magnesium infusions. Fetal heart rates rose in controls at 5-minute intervals and were unchanged in magnesium-treated mothers. Because of disparity of the baseline mean arterial pressure, direct comparisons were not significant before and after cocaine. Alterations from the baseline were different in magnesium-treated versus control animals, with values in the latter rising by 28 +/- 10 mm Hg with lactated Ringer's solution plus cocaine and falling by 3 +/- 5 mm Hg with magnesium pretreatment. Values in test animals originally treated with magnesium rose 4 +/- 11 mm Hg for an overall significance of p less than 0.05. Low beginning serum magnesium levels were associated with ovine hypertension and reduced fetal weight and survival.
Weaver
K
K
Bear Lake Memorial Hospital, Montpelier, Idaho.
Merrell
C L
CL
Griffin
G
G
D000818:Animals; D001792:Blood Platelets / Q000187:drug effects*; D001794:Blood Pressure / Q000187:drug effects; D001808:Blood Vessels / Q000187:drug effects*; D002395:Catecholamines / Q000502:physiology*; D003042:Cocaine / Q000494:pharmacology*; D005260:Female; D005318:Fetal Heart; D006339:Heart Rate / Q000187:drug effects; D008274:Magnesium / Q000097:blood / Q000494:pharmacology*; D010976:Platelet Count / Q000187:drug effects; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D012756:Sheep
D002395:Catecholamines; D008274:Magnesium; D003042:Cocaine