The influence of opioids on local cerebral glucose utilization in the newborn pig.
Topical methionine enkephalin, leucine enkephalin, and dynorphin (10(-6)M) previously have been observed to produce prominent pial arteriolar dilation. Dilation to these opioids could be caused directly by opioids acting on vascular receptors, or indirectly, as a consequence of increased metabolism. Therefore, we examined this possibility by determining the influence of opioids on cerebral glucose utilization in piglets with closed cranial windows using the [14C]deoxyglucose method. Qualitatively, the autoradiographic images expressed as a change in relative optical density from vehicle were unchanged by these opioids. Quantitatively, the opioids similarly had no effect on cerebral glucose utilization (53 +/- 5, 70 +/- 8, 63 +/- 5, and 52 +/- 3, mumol.100 g-1.min-1 for vehicle, methionine enkephalin, leucine enkephalin, and dynorphin, respectively). In contrast, topical glutamate (10(-3) M) produced similar dilation but increased cerebral glucose utilization (41 +/- 3 vs 89 +/- 8 mumol.100 g-1.min-1 for vehicle and glutamate, respectively). Therefore, these opioids do not appear to produce vascular effects through a change in cerebral metabolic utilization of glucose.
Department of Physiology/Biophysics, University of Tennessee, Memphis 38163.
W M
WM
Armstead
R
R
Mirro
S
S
Zuckerman
D W
DW
Busija
C W
CW
Leffler
D000818:Animals; D000831:Animals, Newborn; D001345:Autoradiography; D001921:Brain / Q000378:metabolism*; D004399:Dynorphins / Q000494:pharmacology*; D004743:Enkephalin, Leucine / Q000494:pharmacology*; D004744:Enkephalin, Methionine / Q000494:pharmacology*; D005947:Glucose / Q000378:metabolism*; D013552:Swine; D014018:Tissue Distribution
D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; D004399:Dynorphins; D005947:Glucose