An evaluation of the effects of acute and chronic L-tyrosine administration on BDNF levels and BDNF mRNA expression in the rat brain.

Tyrosinemia type II, which is also known as Richner-Hanhart syndrome, is an inborn error of metabolism that is due to a block in the transamination reaction that converts tyrosine to p-hydroxyphenylpyruvate. Because the mechanisms of neurological dysfunction in hypertyrosinemic patients are poorly known and the symptoms of these patients are related to the central nervous system, the present study evaluated brain-derived neurotrophic factor (BDNF) levels and bdnf mRNA expression in young rats and during growth. In our acute protocol, Wistar rats (10 and 30 days old) were killed 1 h after a single intraperitoneal L-tyrosine injection (500 mg/kg) or saline. Chronic administration consisted of L-tyrosine (500 mg/kg) or saline injections 12 h apart for 24 days in Wistar rats (7 days old), and the rats were killed 12 h after the last injection. The brains were rapidly removed, and we evaluated the BDNF levels and bdnf mRNA expression. The present results showed that the acute administration of L-tyrosine decreased both BDNF and bdnf mRNA levels in the striatum of 10-day-old rats. In the 30-day-old rats, we observed decreased BDNF levels without modifications in bdnf transcript level in the hippocampus and striatum. Chronic administration of L-tyrosine increased the BDNF levels in the striatum of rats during their growth, whereas bdnf mRNA expression was not altered. We hypothesize that oxidative stress can interact with the BDNF system to modulate synaptic plasticity and cognitive function. The present results enhance our knowledge of the pathophysiology of hypertyrosinemia.