Limitations of the technique of pressure microinjection of excitatory amino acids for evoking responses from localized regions of the CNS

J. Lipski*, M. C. Bellingham, M. J. West, P. Pilowsky

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    168 Citations (Scopus)

    Abstract

    The aim of this study, performed on anaesthetized cats and rabbits, was to test the assumption that pressure microinjections of excitatory amino acids cause long-lasting excitation of neurones located close to the injection site. Unitary action potentials on antidromic field potentials were recorded from respiratory or 'reticular' neurones in the medulla oblongata and from phrenic motoneurones at different distances from the injection site. Injection of 10-150 nl (5-150 nmol) of l-glutamate or dl-homocysteic acid into these areas resulted in complex and widespread neuronal events. Generally, more distant neurones (500-1300 μm) were excited for variable periods of time (3-15 min), while neurones in the vicinity of the injection site (0-500 μm) showed, after a brief period of excitation time, a long-lasting (up to 30 min) decrease in excitability or silencing of discharge, probably due to a depolarizing block and disturbances in the ionic composition of the extracellular space. These findings show that interpretation of physiological responses following such injections should not be based on an assumption of local neuronal excitation. Some recommendations regarding the use of this technique are made.

    Original languageEnglish
    Pages (from-to)169-179
    Number of pages11
    JournalJournal of Neuroscience Methods
    Volume26
    Issue number2
    DOIs
    Publication statusPublished - 1988

    Keywords

    • Glutamic acid
    • Homocysteic acid
    • Neuronal excitability
    • Pressure microinjections

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