The Involvement of Bulbospinal Serotonergic Neurons in the Effect of 5-Hydroxytryptophan on Alpha and Gamma Motoneurons

  • N. R. Myslinski
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 294)


As indicated by the work of other investigators, there exists a system of serotonin (5-HT)-containing neurons which originate in the nucleus raphe and terminate near motoneurons in the spinal cord (Carlsson et al., 1964; Dahlström and Fuxe, 1965; Anderson and Holgerson, 1966). It has also been shown that the i.v. administration of the 5-HT precursor, 5-hydroxytryptophan (5-HTP), leads to the facilitation of both alpha and gamma motoneurons (Myslinski and Anderson, 1978). The general belief is that 5-HTP produces this effect via the bulbospinal 5-HT pathway which converts it to 5-HT and subsequently releases it to activate the postsynaptic receptor sites (Anderson, 1972). If 5-HTP does produce this effect via the 5-HT neurons, the concurrent use of a 5-HT reuptake inhibitor should potentiate its effects; pre-treatment with a 5-HT synthesis inhibitor should depress its effects; and the electrical stimulation of the bulbospinal 5-HT system should produce effects similar to that of 5-HTP. We found all three cases to be true, which argues that 5-HTP works via the 5-HT pathway to facilitate alpha and gamma motoneurons.


Nucleus Raphe Gamma Activity Spinal Cord Dorsal Horn Gallamine Triethiodide Gamma Motoneuron 
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  1. Anderson, E.G., 1972, Bulbospinal serotonin-containing neurons and motor control, Fed. Proc., 31: 107–112.PubMedGoogle Scholar
  2. Anderson, E.G., and Holgerson, L.O., 1966, The distribution of 5-hydroxy-tryptamine and norepinephrine in the cat spinal cord, J. Neurochem., 13: 479–485.PubMedCrossRefGoogle Scholar
  3. Carlsson, A., Corrodi, H., Fuxe, K., and Hökfelt, 1969, The effect of anti-depressant drugs in the depletion of intraneuronal brain 5-HT stores caused by 4-methyl alpha-ethyl metatyramine, Eur. J. Pharmacol., 5: 357–363.PubMedCrossRefGoogle Scholar
  4. Carlsson, A., Falck, B., Fuxe, K., and Hillarp, N.A., 1964, Cellular localization of monoamines in the spinal cord, Acta Physiol. Scand., 60: 112–119.PubMedCrossRefGoogle Scholar
  5. Dahlström, A., and Fuxe, K., 1965, Evidence for the existence of monoamine neurons in the central nervous system. II. Experimentally induced changes in the intraneuronal amine levels of bulbospinal neuron systems, Acta Physiol. Scand., Suppl. 247, 64: 1–36.CrossRefGoogle Scholar
  6. Fields, H.L., Basbaum, A.L., Clanton, C.H., and Anderson S.D., 1977, Nucleus raphe magnus inhibition of spinal cord dorsal horn neurons, Brain Res., 126: 441–453.PubMedCrossRefGoogle Scholar
  7. Koe, B.K., and Weissman, A., 1968, p-Chlorophenylalanine: a specific depletor of brain 5-HT, Adv. Pharmacol., 6B: 27–29.Google Scholar
  8. Myslinski, N.R., and Anderson, E.G., 1978, The effect of precursors on alpha and gamma motoneuron activity. J. Pharmacol. Exp. Therap., 204: 19–26.Google Scholar
  9. Proudfit, H.K., and Anderson, E.G., 1974, New long latency bulbospinal evoked potentials blocked by serotonin antagonists, Brain Res., 65: 542–546.PubMedCrossRefGoogle Scholar
  10. Taber, C.A., and Anderson, E.G., 1973, Paradoxical blockade by p-chloro-phenylalanine of 5-hydroxytryptophan facilitatory actions on spinal reflexes, J. Pharmacol. Exp. Therap., 187: 229–238.Google Scholar

Copyright information

© Plenum Press, New York 1991

Authors and Affiliations

  • N. R. Myslinski
    • 1
  1. 1.Department of PhysiologyUniversity of Maryland School of MedicineBaltimoreUSA

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