Effects of Sufentanil on Regional Cerebral Glucose Utilization in Rats

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Abstract
Sufentanil, a narcotic 5 to 10 times more potent than fentanyl, reduces cortical cerebral blood flow and O2 consumption in rats, with seizure activity occurring in some animals. The effects of sufentanil on blood flow and metabolism in subcortical structures have not been defined clearly. The present study examines the effects of i.v., sufentanil (40 or 160 .mu.g/kg) on regional cerebral glucose utilization (r-CMRgl) in paralyzed, mechanically ventilated rats using 2-deoxy-D-[14C]glucose and autoradiography. Regional cerebral glucose utilization was decreased in all cortical areas examined in rats receiving either dose of sufentanil; the larger dose of sufentanil (160 .mu.g/kg) decreased r-CMRgl in cortical structures 20-45% below control values. Subcortical structures (2), the caudate nucleus and the ventral thalamic nucleus, manifested a 39-54% decrease in r-CMRgl at each dose of sufentanil. Limbic system structures responded differently. Sufentanil 40 .mu.g/kg produced focal areas of markedly increased r-CMRgl in the amygdala of 2 of 6 rats; sufentanil 160 .mu.g/kg produced marked increases in r-CMRgl in focal areas of hippocampus (4 of 8 rats) and amygdala (7 of 8 rats). EEG activation suggestive of seizure activity was evident in the 2 low-dose sufentanil and 6 of the 7 high-dose sufentanil rats that had focally increased r-CMRgl in the amygdala. Sufentanil causes a selective increase in r-CMRgl in subcortical limbic nuclei, particularly the amygdala, in the rat. EEG patterns of seizure activity may reflect subcortical, rather than cortical activation.