It is important to elucidate the mechanism of dysautonomias in patients with Parkinson's disease; therefore, this study aimed to investigate the cardiovascular and autonomic changes that occur in an animal model of Parkinsonism. Adult male Wistar rats were anesthetized before bilateral microinfusions of 6-hydroxydopamine (6-OHDA) into the substantia nigra. The sham group underwent the same surgical procedure but received vehicle. After 7 days, the mean arterial pressure (MAP) and heart rate (HR) were measured, and various drugs were injected into conscious rats through cannulas previously implanted in the femoral artery and vein. Spectral analyses of systolic arterial pressure (SAP) and pulse interval (PI) were conducted with the CardioSeries software as the spontaneous baroreflex gain and effectivity. The animals were subjected to ␣-, ␤-adrenergic, or muscarinic receptor antagonism. For confirmation of the lesion, the levels of dopamine in the striatum were quantified by high-performance liquid chromatography. Animals that underwent 6-OHDA microinfusion had lower MAP and HR compared with those in the sham group. Spectral analysis of SAP showed that 6-OHDA animals exhibited a decrease in the sympathetic component. The PI values did not differ between groups. After the administration of muscarinic and ␤-adrenergic antagonists, the cardiovascular measures did not differ between the groups. However, upon administration of the ␣-adrenergic antagonist, the 6-OHDA animals exhibited a lower decrease in the MAP. We report cardiovascular impairments in 6-OHDA animals, possibly due to decreased sympathetic activity. Determination of the origin of these changes (central or peripheral) requires further investigation. sympathetic; parasympathetic; prazosin; spectral analysis; dopamine; baroreflex PARKINSON'S DISEASE (PD) is characterized by a decrease in striatal dopamine (DA) levels due to the death of neurons in the substantia nigra pars compacta (SNpc). After an 80% decrease of DA levels in the striatum, the classic motor symptoms of PD appear (11,38). These include bradykinesia, rigidity, tremor, and postural instability (29). Although the motor signs of PD are well studied and recognized, symptoms of dysautonomia, despite being reported at all stages of PD, are rarely considered clinically even if they are the main complaint. Dysautonomia considerably impairs the quality of life in the early stages, and it can be debilitating with advancing disease (7,8).Cardiovascular involvement is very common in patients with PD (21, 24). Orthostatic hypotension (OH), postprandial hypotension, as well as cardiac arrhythmias, livedo reticularis, and leg edema are commonly reported (26,43). OH is the most reported symptom with a prevalence of up to 58% in patients with PD (18,24). However, despite all of the speculation, the pathophysiology of OH, as well as the severity of hemodynamic compromise, remains controversial. This has been associated with a central disorder that impacts the medulla, namely, the involvement of both the centra...