Abstract
To clarify the mechanism (s) responsible for nausea and vomiting induced by L-dopa administration, dopamine levels in the plasma and lymph of rats were investigated in the 60-min period following an intravenous bolus of L-dopa (2.5 mg/kg body weight). The dopamine level in plasma from the femoral artery was the highest at 5 min immediately after the L-dopa injection, and was eliminated thereafter. Showing the same tendency as the plasma, the lymph from the thoracic duct showed a maximal increase of dopamine at 0 to 10 min, and a rapid decrease later. In contrast, the dopamine level in the lymph from the cervical lymph trunk increased, peaked at 10 to 20 min, and fell gradually thereafter. The dopamine level in the cervical lymph was higher than that in the thoracic lymph. When these data were kinetically analyzed, the cervical lymph had a larger area under the dopamine concentration-time curve than the thoracic lymph. Both the cervical lymph and the thoracic lymph had longer values of dopamine mean residence time than the plasma. Our findings revealed that when L-dopa was administered with an intravenous bolus, dopamine was higher and remained longer in the cervical lymph than in the rest of the body.
