The effect of intrastriatal injection of liposome-entrapped tyrosinase on the dopamine levels in the rat brain

Parkinson's disease is a neurodegenerative disorder which is mainly charact erized by degeneration of the dopaminergic cells in the ni,oro-striatal sys tem. Due to a lowered L-tyrosine 3-monooxygenase activity, L-tyrosine is no t sufficiently transformed to L-DOPA, To date the most common therapy is th e administration of the dopamine precursor L-DOPA, with severe collateral e ffects. Therefore, the substitution of the lacking tyrosine hydroxylase wit h tyrosinase might be a novel therapeutical approach that would generate sp ecifically L-DOPA from L-tyrosine. We present here evidence that stereotaxi c injection of liposome-entrapped tyrosinase is able to significatively inc rease the levels of dopamine in the rat brain. The catecholamines L-DOPA, d opamine, L-epinephrine, L-norepinephrine were extracted by acid treatment f rom the brains and detected by HPLC.