Brain Structure and Function

, Volume 217, Issue 2, pp 395–409

Comparison of the effects of acute and chronic administration of ketamine on hippocampal oscillations: relevance for the NMDA receptor hypofunction model of schizophrenia

  • Kara Kittelberger
  • Elizabeth E. Hur
  • Saba Sazegar
  • Vidya Keshavan
  • Bernat Kocsis
Original Article

DOI: 10.1007/s00429-011-0351-8

Cite this article as:
Kittelberger, K., Hur, E.E., Sazegar, S. et al. Brain Struct Funct (2012) 217: 395. doi:10.1007/s00429-011-0351-8

Abstract

The proper organization and function of GABAergic interneuron networks is essential for many cognitive processes and abnormalities in these systems have been documented in schizophrenic patients. The memory function of the hippocampus depends on two major patterns of oscillations in the theta and gamma ranges, both requiring the intact functioning of the network of fast-firing interneurons expressing parvalbumin. We examined the ability of acute and chronic administration of NMDA receptor (NMDA-R) antagonists to recapitulate the oscillatory dysfunctions observed in schizophrenia. In freely moving rats, acute injection of MK801 or ketamine increased gamma power in both CA1 and dentate gyrus of the hippocampus. Theta peak shifted to higher frequencies whereas the average 5–10 Hz theta power decreased by 24% in CA1 and remained high in the dentate gyrus. Strong increase in CA1 gamma and decrease in theta power triggered by brainstem stimulation were found under urethane anesthesia. In contrast to acute experiments, chronic administration of ketamine caused a steady decline in both gamma and theta oscillations, 2–4 weeks after treatment. A further important difference between the two models was that the effects of acute injection were more robust than the changes after chronic treatment. Chronic administration of ketamine also leads to decrease in the number of detectable parvalbumin interneurons. Histological examination of interindividual differences indicated, however, that within the ketamine treated group a further decrease in parvalbumin neurons correlated with strengthening of oscillations. The findings are consistent with abnormalities of oscillations in human schizophrenia and further validate the NMDA-R hypofunction hypothesis.

Keywords

MK-801 Theta rhythm Gamma rhythm Parvalbumin Interneurons Electroencephalography 

Copyright information

© Springer-Verlag (outside the USA) 2011

Authors and Affiliations

  • Kara Kittelberger
    • 1
  • Elizabeth E. Hur
    • 1
  • Saba Sazegar
    • 1
  • Vidya Keshavan
    • 1
  • Bernat Kocsis
    • 1
  1. 1.Department of PsychiatryBeth Israel Deaconess Medical Center, Harvard Medical SchoolBostonUSA