Hemodynamic effects of clonidine in two contrasting models of autonomic failure: multiple system atrophy and pure autonomic failure.

摘要: We assessed the effects of clonidine on blood pressure (BP) and heart rate (HR) in multiple system atrophy (MSA), where autonomic nervous lesion site is preganglionic, pure failure (PAF), it postganglionic. In normal subjects, intravenous infusion selective alpha2-adrenoceptor agonist reduces BP plasma noradrenaline (NA) levels by means central action, as well inducing growth hormone (GH) release. Clonidine-induced GH release impaired MSA but spared PAF. However, hemodynamic have not been studied extensively these disorders. examined test results (performed our laboratories using London Autonomic Units protocol) 58 patients: 39 with probable 19 Systolic (SBP), diastolic (DBP), HR, NA were measured supine at baseline for up to 60 minutes after clonidine. Clonidine resulted a significant fall patients, which occurred earlier (within 15 clonidine) greater extent than seen PAF patients. patients showed reduction HR administration, although this finding was significantly decreased administration both groups. Although basal lower there no difference relative between negative correlation response groups The vasodepressor action suggests that partial preservation brainstem sympathetic outflow pathways may reflect its sites spinal cord part functionally preserved MSA. Despite similar degrees effect attenuated compared This attenuation peripheral denervation supersensitivity due postganglionic site. These differences, thus, underlying PAF, data help differentiate conditions.