Abstract
There is an ongoing controversy about potential toxicity of L-3,4-dihydroxyphenylalanine (L-dopa) to dopaminergic neurons in Parkinson's disease (PD). Neuroimaging data suggest that L-dopa accelerates the loss of dopamine nerve terminals, especially at higher doses. The disputed aspect of toxicity and the frequently observed motor complications accompanying L-dopa therapy have led to an increased use of dopamine agonists during the past two decades. Reports describing their neuroprotective potential to dopaminergic neurons have attracted much attention. Here, we describe the novel finding that the combination of a dopamine (DA) agonist, alpha-dihydroergocryptine (DHEC), with L-dopa or DA exerts a synergistic stimulatory effect on dopaminergic neurons in primary culture, while each substance alone had no or less effect. DA receptor stimulation plays a decisive role. The synergistic effect suggests that a combinatory therapy can be beneficial to slow the degeneration of dopaminergic neurons.