L-Dopa-Induced Hypotension: Depression of Spinal Sympathetic Neurons by Release of 5-Hydroxytryptamine

  • Donald N. Franz
  • Robert J. Neumayr
  • Bradford D. Hare
Part of the Advances in Experimental Medicine and Biology book series (AEMB)


In studies designed to determine the respective functional roles of two bulbospinal monoaminergic pathways to sympathetic preganglionic neurons, both L-dopa and precursors of 5-HT depressed transmission through excitatory spinal reflex and bulbospinal sympathetic pathways. Transmission through spinal reflex pathways was secondarily enhanced after L-dopa. Pharmacological tests indicated mediation of these effects by monoamines. After antagonism or depletion of central 5-HT, L-dopa only enhanced transmission through both pathways. The results indicate that hypotension and other sympathoinhibitory effects of L-dopa are produced at the spinal level by release of 5-HT from terminals of bulbospinal 5-HT pathways that are inhibitory to sympathetic preganglionic neurons. The excitatory effects of L-dopa are apparently mediated by release of catecholamines from bulbospinal noradrenergic pathways that are excitatory.


Sympathetic Nerve Activity Depressant Effect Excitatory Effect Reflex Pathway Sympathetic Discharge 
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Copyright information

© Plenum Press, New York 1977

Authors and Affiliations

  • Donald N. Franz
    • 1
  • Robert J. Neumayr
    • 1
  • Bradford D. Hare
    • 1
  1. 1.Department of PharmacologyUniversity of Utah College of MedicineSalt Lake CityUSA

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