Neurophysiological consequences of presynaptic receptor activation: changes in noradrenergic terminal excitability

Shoji Nakamura, James M. Tepper, Stephen J. Young, Philip M. Groves

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50 Scopus citations


Experiments were carried out to explore the view that activation of presynaptic receptors on the terminals of noradrenergic neurons is accompanied by alterations in their excitability to direct electrical stimulation. Antidromic action potentials evoked from frontal cortex of urethane anesthetized rats were recorded extracellularly from nucleus locus coeruleus. The threshold current necessary to evoke antidromic action potentials varied as a result of infusion of adrenergic agonist and antagonists into frontal cortex within 50 μm of the stimulating electrode. Local infusion of the α-adrenergic agonist clonidine produced a marked decrease in terminal excitability, while the α-antagonist phentolamine produced an increase in terminal excitability and was shown to reverse the effect of the agonist. Infusion of the β-adrenergic agonist isoproterenol was without effect, although the β-antagonist propranolol resulted in a decrease in terminal excitability. Infusions of potassium increased excitability of locus coeruleus terminals. Terminal excitability was seen to vary inversely with the rate of spontaneous or high frequency stimulation-induced firing of locus coeruleus neurons. From these observations, it may be inferred that activation or blockade o f α-adrenergic presynaptic receptors results in changes in polarization and/or conductance of the noradrenergic synaptic endings. These results are discussed with respect to phenomena associated with the possible presynaptic regulation of neurotransmitter release.

Original languageEnglish (US)
Pages (from-to)155-170
Number of pages16
JournalBrain research
Issue number1-2
StatePublished - Dec 7 1981
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology


  • neurotransmitter release
  • noradrenergic terminals
  • presynaptic receptors

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