Mesolimbic dopaminergic system is involved in diurnal blood pressure regulation

Parkinson's disease (PD) patients with autonomic failure show no nocturnal decrease in blood pressure (BP). At present, it is not clear if this symptom is attributable to the disturbance of the dopaminergic (DA) system that is responsible for PD. In the present study, we determined that the mesolimbic DA system is involved in diurnal profiles of the mean BP (MBP) by destroying the A10 DA system in rats with 6-hydroxydopamine. In control rats, a clear dip in the MBP and heart rate (HR) occurs during the light, that is, resting period, analogous to the nocturnal dip in normal humans. This normal daytime decrease in MBP and HR was disturbed by inducing a lesion of the ventral tegmental area (VTA) DA neurons, although the rhythms of wake-sleep duration and behavioral activity remained relatively intact. On the basis of this evidence, the absence of a nocturnal dip in BP in PD patients is attributed to impairment of the mesolimbic DA system.