MK-771 enhances the turnover of norepinephrine in brain

Single injection of MK-771, an analog of thyrotropin-releasing hormone (10 mg/kg) increased the soluble tyrosine hydroxylase activity in striatum and olfactory tubercles by 22% and 31%. The endogenous levels of norepinephrine in olfactory tubercles, striatum, hypothalamus, mid-brain, pons medulla and cerebral cortex remained unchanged; in hippocampus, it was lowered to 71% of controls. Furthermore, the concentration of 3-methoxy-4-hydroxy-phenylethylene glycol was enhanced by 33%. Data suggest that MK-771 increases the synthesis and release of norepinephrine and that MK-771 elicits its CNS stimulant action partly by augmenting the turnover of this biogenic amine.