Aging causes alterations in neurotransmitter content and metabolism that may explain changes in physiological functions with age. In the last decade a great deal of attention has focused on the alteration of neurotransmitter levels by dietary manipulation. However, these studies have concentrated mainly on young adult animals. Our preliminary studies in old rats indicate that protein deficiency induces an increase in dopamine in the neostriatum. The objectives of this study are: 1) to study the timing of this increase in old rats and the duration of the effect; 2) to determine if this phenomenon also occurs in young adult rats and if so, the timing and the duration of the effect; and 3) to elucidate the mechanism(s) by which a low protein diet increases dopamine in the corpus striatum of aged rats, i.e. changes in tyrosine uptake, dopamine synthesis, and turnover rate of dopamine. The long term goals of these studies are related to the treatment of Parkinson's disease, a condition characterized by a reduction of dopamine in the neostriatum.
