The use of bromocriptine for testing central dopaminergic reactivity.

A single oral intake of 10 mg of Bromocriptine can modify both plasma renin activity (PRA) and arterial blood pressure (BP). The changes in both variables depend on the integrity of the central dopaminergic systems. The parkinsonians whose extrapyramidal symptoms are markedly improved by L-Dopa in association with a decarboxylase inhibitor (IDC) and the untreated parkinsonians are the only patients whose PRA and BP are lowered 1 h after Bromocriptine ingestion. The results obtained in the L-dopa-induced dyskinetic parkinsonians are similar to those obtained in the group of L-Dopa-resistant patients. This points to the paradoxical hypothesis of dopaminergic hyposensitivity in the dyskinetic patients. In spite of the absence of correlation between PRA and BP, it is possible that lowering of BP by Bromocriptine is linked to the parallel decrease of PRA. An increase of the BP may be obtained in the dyskinetic and L-Dopa-resistant groups. These data point to a possible involvement of central dopaminergic systems in some aspects of hypertension.