Abstract
Postural hypotension is often seen during treatment with l-dopa in patients with parkinsonism. In view of the possibility that this effect might be related to sympathetic impairment, the chronotropic responses to pre- and postganglionic cardioaccelerator nerve stimulation (1-30 cps) and to i.v. norepinephrine (0.3-10 µg/kg) were compared before and three to six hours after a single i.v. injection of l-dopa (100 mg/kg). Injection of l-dopa led to an increase in heart rate lasting for an average of four hours, and to an initial rise followed by a fall in systemic arterial pressure. Chronotropic responses to both cardioaccelerator nerve stimulation and norepinephrine were significantly reduced after l-dopa. Because administration of l-dopa produced acidosis, sodium bicarbonate was given i.v. to maintain blood pH within physiologic range; this did not affect the magnitude of impairment in chronotropic responses to cardioaccelerator nerve stimulation produced by l-dopa but the degree of impairment in chronotropic responses to norepinephrine was significantly reduced. Systemic pressor responses to norepinephrine decreased after l-dopa only in those experiments in which acidosis was present. These data suggest that l-dopa interferes with postganglionic nerve function.
Footnotes
- Received August 20, 1970.
- Accepted December 28, 1970.
- © 1971 by The Williams & Wilkins Co.
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|