Innate differences in medial septal area burst firing neurons and the hippocampal theta rhythm during ambulation in selectively bred rat lines

Timothy E. Breen, Sandra L. Morzorati

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9 Scopus citations


Previous studies have demonstrated a higher mean peak frequency of the hippocampal (HPC) theta rhythm during REM sleep in alcohol-nonpreferring (NP) rats when compared with alcohol-preferring (P) rats. Burst firing neurons of the medial septal area (MS/VDB) are thought to pace the HPC theta rhythm during REM sleep and ambulation. Therefore, extracellular action potentials of MS/VDB burst firing neurons and HPC-CA1 field potentials were recorded simultaneously in ambulating P and NP rats. These recordings revealed that the mean peak frequency of the HPC theta rhythm during ambulation was higher in NP rats (7.62 ± 0.12 Hz) as compared with P rats (7.21 ± 0.14 Hz) (P < 0.05). Consistent with the difference in the HPC theta rhythm, the burst pattern of MS/VDB neurons exhibited a shorter inter-burst interval in the NP rats (NP 82.4 ± 5.4 ms, P 97.4 ± 8.1 ms, P < 0.05). The difference in the inter-burst interval was confirmed by the distribution of inter-spike intervals in cumulative inter-spike interval histograms and the frequency of peaks in the mean cumulative autocorrelation histograms for P and NP rats. The mean cumulative autocorrelation histograms for P and NP rats also revealed that the regularity of the burst pattern in NP rats was sustained over a longer time period as determined by the decay constant. The cross-correlation of MS/VDB burst activity and the HPC theta rhythm showed a strong relationship between the two signals in P and NP rats. In both P and NP rats, two similar phase relationships were observed between MS/VDB bursting neurons and the HPC theta rhythm. These findings are in agreement with the hypothesis that MS/VDB burst firing neurons are responsible for the variation in the HPC theta rhythm between the two lines. Other mechanisms consistent with these findings are also discussed.

Original languageEnglish (US)
Pages (from-to)156-164
Number of pages9
JournalBrain research
Issue number1-2
StatePublished - Apr 1 1996



  • Alcohol-nonpreferring rat
  • Alcohol-preferring rat
  • Burst activity
  • Hippocampus
  • Medial septum
  • Theta rhythm
  • Vertical limb of the diagonal band of Broca

ASJC Scopus subject areas

  • Neuroscience(all)

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