Chemical modulation of ephaptic activation of CA3 hippocampal pyramids

DALKARA T., Krnjević K., Ropert N., Yim C.

Neuroscience, vol.17, no.2, pp.361-370, 1986 (Scopus) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 17 Issue: 2
  • Publication Date: 1986
  • Doi Number: 10.1016/0306-4522(86)90252-6
  • Journal Name: Neuroscience
  • Journal Indexes: Scopus
  • Page Numbers: pp.361-370
  • Hacettepe University Affiliated: Yes


In rats under urethane anaesthesia, antidromic population spikes were evoked in CA3 pyramidal layer by fimbrial/commissural stimulation at a very low frequency (~ 0.5 Hz). Submaximal population spikes - between 20 and 90% of maximum - were enhanced by 8-38% by applications of acetylcholine and bicuculline, or by medial septal stimulation. Noradrenaline had a less pronounced and regular facilitatory action, whereas γ-aminobutyrate and glutamate only depressed population spikes. Maximal enhancement by acetylcholine or bicuculline was observed when the antidromic population spike was initially at 38-53% of maximum amplitude. A simple explanation of these results is that acetylcholine and bicuculline, by raising their excitability, facilitate the excitation of non-invaded pyramidal cells by antidromic field potentials. They are fully in keeping with previous intracellular observations on ephaptic interactions between CA3 neurons, and provide a further illustration, in situ, of the importance of increased excitability and disinhibition-whether caused by drugs or synaptic action-in promoting synchronized excitation by ephaptic currents. © 1986.