Abstract:
The administration of 3,4-dihydroxyphenylalanine (L-Dopa) has been shown to result in the facilitation of performance while the administration of 5-hydroxytryptophan (5-HTP) results in an impairment of performance and reported enhancement of acquisition. The purpose of the present study is to compare the effects of 5-HTP and L-Dopa on the acquisition of a single behavioral task.
Each animal received a total of twenty daily trials in a shuttle box one hour after injection. All mice learned to avoid footshock both during each trial and the inter-trial interval. The results indicate that 5-HTP and L-Dopa do not facilitate the acquisition of a conditioned avoidance task. A significant number of inter-trial crossovers was obtained for the L-Dopa group for the 13 days of training and the 5-HTP group for the first 2 days.
It was concluded that possible peripheral effects of L-Dopa interfered with acquisition. It was suggested that the effects of 5-HTP upon the visual system might have served to inhibit acquisition of a visual task. In view of the subject x treatment interaction, it would appear that the metabolites of 5-HTP and L-Dopa produced effects which varied within subjects as a function of the daily administration of precursors.
The further analysis of effects of 5-HTP and L-Dopa on acquisition should include correlations between variations in regional concentrations and specific behaviors.
