Intravenous l-DOPA Plus Carbidopa in Depressed Patients: Average Evoked Response, Learning, and Behavioral Changes

Publisher Website
Google Scholar
Abstract
The peripheral decarboxylase inhibitor carbidopa allowed safe i.v. administration of L-dopa in amounts sufficient to alter cortical average evoked response (AER) and learning function in 13 depressed patients. The apparently rapid conversion of L-dopa to dopamine is consistent with the 20-30 min onset of effects. Unipolar and bipolar depressed patients responded differently to the alteration in brain biogenic amines and also to the nonspecific stress of the experiment. I.v. L-dopa had effects on the AER that were similar to those with oral dopa given chronically, an augmentation of amplitude-intensity slopes in unipolar patients and a relative reduction of slopes in bipolar patients. I.v. L-dopa did not enhance verbal learning as did chronic oral treatment, but rather was associated with reduced learning compared with placebo infusions. Different neurochemical changes following L-dopa given in single i.v. doses may be responsible for the different learning and behavioral changes from those found previously with oral dopa administered chronically.