MS produces an excitatory state when injected intravenously into concious pigs, resulting in a rise in metabolic rate. Prostanoids play an important role in the regulation of cerebral hemodynamics, particularly in newborn animals. The effects of MS infusion on systemic and cerebrovascular prostanoid levels were examined in 1-3 day old concious newborn piglets (n=6) which received a bolus of 100 μg/kg over 5 minutes, followed by a continuous i.v. infusion (100 μg/kg/hr) for 4 hours. The control animals received an equivalent volume bolus and infusion of 5% dextrose. Blood samples from the carotid artery and sagittal sinus vein were collected before, during (0.5, 1, 2, 3 & 4 hr), and post (1 & 2 hr) infusion for determination of prostaglandin E2 (PGE2) and thromboxane B2 (TxB2) by enzyme immunoassay. There was a significant increase in systemic PGE2 following the bolus dose (614.8±100.9 pg/ml), compared to baseline levels (159.2±54.2 pg/ml, p<0.001). However, at 1 hr of continuous infusion, systemic PGE2 levels fell substantially(49.7±39.7 pg/ml, p<0.01 vs baseline), and remained attenuated throughout the 4-hour infusion time, and up to 2 hours post infusion (p<0.05 to p<0.001). In contrast, sagittal sinus vein PGE2 levels increased significantly after the bolus dose(888.5±210.5 pg/ml, p<0.05), and at 4 hours of infusion(1420.6±192.3 pg/ml, p<0.001) vs baseline (107.3±58 pg/ml). Systemic TxB2 levels remained similar to baseline(436±85.1 pg/ml) until 4 hours of infusion (1175.3±182.1 pg/ml,p<0.001). Sagittal sinus vein TxB2 levels increased following the bolus dose (876±187.5 pg/ml, p<0.01) and at 1 hour of infusion (798.3±230.3 pg/ml, p<0.05) compared to baseline (271±189.6 pg/ml). However, from 2 to 4 hours of infusion, and up to 2 hours post infusion, it returned to baseline values. Continuous infusion of MS in the concious newborn piglet causes significant changes in systemic and cerebrovascular prostanoid levels. These changes may be associated with alterations in cerebrovascular perfusion and metabolic activity.
