Effect of cocaine on rat brain enzymes

Acute administration of cocaine (20 mg/kg, i.p.) stimulated activity of striatal tyrosine hydroxylase (TH) which reached its maximum level at 10 min and returned to normal between 20-40 min. However, tryptophan hydroxylase (TPH) activity in the pons-medulla was reduced to a minimum at 10 min after its injection and returned to normal between 20-40 min. Activity of monoamine oxidase (MAO) was significantly reduced at 10 min and increased MAO (Type A) at 20 min showing a biphasic effect of cocaine on this enzyme. Relation of the time-courses of cocaine effects on the activity of these enzymes and the levels of related neurotransmitters is discussed.