Sensitivity of transformed (phasic to tonic) motor neurons to the neuromodulator 5-HT

B. Griffis, P. Bonner, R. L. Cooper

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Long-term adaptation resulting in a 'tonic-like' state can be induced in phasic motor neurons of the crayfish, Procambarus clarkii, by daily low-frequency stimulation [Lnenicka, G.A., Atwood, H.L., 1985b. Long-term facilitation and long-term adaptation at synapses of a crayfish phasic motoneuron. J. Neurobiol. 16, 97-110]. To test the hypothesis that motor neurons undergoing adaptation show increased responses to the neuromodulator serotonin (5-HT), phasic motor neurons innervating the deep abdominal extensor muscles of crayfish were stimulated at 2.5 Hz, 2 h/day, for 7 days. One day after cessation of conditioning, contralateral control and conditioned motor neurons of the same segment were stimulated at 1 Hz and the induced excitatory post-synaptic potentials (EPSPs) were recorded from DEL1 muscle fibers innervated by each motor neuron type. Recordings were made in saline without and with 100 nM 5-HT. EPSP amplitudes were increased by 5-HT exposure in all cases. Conditioned muscles exposed to 5-HT showed a 2-fold higher percentage of increase in EPSP amplitude than did control muscles. Thus, the conditioned motor neurons behaved like intrinsically tonic motoneurons in their response to 5-HT. While these results show that long-term adaptation (LTA) extends to 5-HT neuromodulation, no phenotype switch could be detected in the postsynaptic muscle. Protein isoform profiles, including the myosin heavy chains, do not change after 1 week of conditioning their innervating motor neurons.

Original languageEnglish
Pages (from-to)495-504
Number of pages10
JournalComparative Biochemistry and Physiology - A Molecular and Integrative Physiology
Volume127
Issue number4
DOIs
StatePublished - 2000

Bibliographical note

Funding Information:
Funding was provided by NIH-NIMH Behavioral ecology and comparative neurobiology training grant (B.G), NSF grants IBN-9808631 (R.L.C.) and ILI-DUE-9850907 (R.L.C.).

Keywords

  • 5-HT
  • Crayfish
  • Motor neuron
  • Muscle
  • Neuromodulator
  • Phasic
  • Tonic

ASJC Scopus subject areas

  • Biochemistry
  • Physiology
  • Molecular Biology

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