EFFECT OF MORPHINE ON CEREBRAL GLYCOLYTIC INTERMEDIATES AND ENZYMES OF RATS IN VITRO

Morphine caused a stimulation of glucose utilization in rat cerebral homogenates after a 30-min lag period. The fructose diphosphate concentration of the incubation medium in the presence of morphine in vitro was higher after 60 min of incubation, while the concentration of pyruvate was lower at both 30 and 60 min than those in the absence of morphine. Adenosine monophosphate (AMP) concentration was lower and the adenosine triphosphate (ATP) level was higher in the presence than in the absence of morphine after 30 and 60 min of incubation. The concentration of glyceraldehyde-3-P was decreased while the level of 3-P-glycerate was increased by morphine, indicating a facilitation of the glyceraldehyde-3-P dehydrogenase step of glycolysis. AMP inhibited the activity of glyceraldehyde-3-P dehydrogenase appreciably in rat cerebral homogenates. The initial facilitation by morphine is thought to be at the glyceraldehyde-3-P dehydrogenase step due to the low AMP concentration and a secondary facilitation at the P-fructokinase step due to the accumulated concentrations of ATP and fructose diphosphate. Additionally, the time required to alter adenine nucleotide concentrations may explain the lag period that occurs before the stimulation of glucose utilization by morphine is manifested. © 1969.