Effect of L‐threo‐3,4‐dihydroxy‐phenylserine on muscle sympathetic nerve activities in Shy‐Drager syndrome

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Abstract
We observed changes in postganglionic efferent discharges of muscle sympathetic nerve (muscle sympathetic activity, MSA) microneurographically before and after the oral administration of L-threo-3,4-dihydroxyphenylserine (L-threo-DOPS), a precursor of norepinephrine, in a patient with Shy-Drager syndrome and irregular fluctuations of blood pressure. Before drug administration, MSA was only rarely observed with the patient in the supine position. There was a slight increase in MSA during head-up tilting to 40.degree. , and orthostatic hypotension (OH) occurred just after the body was tilted head upward to 40.degree.. MSA became prominent 30 minutes after the oral administration of 200 mg of L-threo-DOPS while the patient was in a 40.degree. head-up position, and the OH was improved. The MSA discharge rate decreased and OH reappeared 3 hours after oral administration, when the plasma concentration of norepinephrine was at its highest level. We suggest that the OH improved mainly because of the increase in MSA due to L-threo-DOPS, and that the drug may activate sympathetic outflow at a site proximal to the sympathetic ganglion.