Parvalbumin-immunoreactive, fast-spiking neurons in the medial septum/diagonal band complex of the rat: intracellular recordings in vitro

Neuroscience. 1999;92(2):589-600. doi: 10.1016/s0306-4522(99)00026-3.


The medial septum/diagonal band complex is composed predominantly of cholinergic and GABAergic neurons, and it projects to the hippocampal formation. A proportion of the GABAergic neurons contain parvalbumin, a calcium-binding protein that has previously been localized in fast-spiking, non-accommodating GABAergic neurons in the cerebral cortex and neostriatum. The aim of the present study was to determine whether parvalbumin is localized preferentially in a similar electrophysiological class of neuron in the medial septum/diagonal band complex. The study was carried out using in vitro intracellular recording, intracellular biocytin filling and parvalbumin immunocytochemistry. Three main classes of neurons were identified according to standard criteria: burst-firing, slow-firing and fast-firing neuronal populations. The fast-firing neurons were subdivided into two subpopulations based on whether or not they displayed accommodation. The fast-spiking, non-accommodating cells were furthermore found to be spontaneously active at resting potentials, and to possess action potentials of significantly (P < 0.05) shorter duration (half width: 0.61 +/- 0.12 ms) than those of the regular-spiking, accommodating neurons (1.0 +/- 0.34 ms). Of the neurons that were successfully filled with biocytin and processed for parvalbumin immunoreactivity, 82% of the fast-spiking, non-accommodating cells possessed parvalbumin immunoreactivity, while none of the regular-spiking, accommodating neurons were found to be immunoreactive for parvalbumin. The slow-firing neurons, shown previously to be cholinergic, did not stain for parvalbumin immunoreactivity, in agreement with studies showing parvalbumin to be localized solely in GABAergic neurons in the medial septum/diagonal band complex. In conclusion, these findings suggest the presence of a previously uncharacterized population of neurons in the medial septum/diagonal band complex that generate high-frequency, non-adaptive discharge. This property correlates with the localization of parvalbumin in these neurons, which suggests that parvalbumin fulfils the same role in the medial septum/diagonal band complex that it does in other parts of the brain. The fast-spiking neurons in the medial septum/diagonal band complex may play an essential role in the GABAergic influence of the septum on the hippocampal formation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / physiology*
  • Animals
  • Calcium-Binding Proteins / analysis*
  • Calcium-Binding Proteins / physiology
  • Cholinergic Fibers / chemistry
  • Cholinergic Fibers / physiology
  • Limbic System / chemistry*
  • Limbic System / physiology
  • Lysine / analogs & derivatives
  • Lysine / analysis
  • Nerve Tissue Proteins / analysis*
  • Nerve Tissue Proteins / physiology
  • Neurons / chemistry*
  • Neurons / physiology
  • Parvalbumins / analysis*
  • Parvalbumins / physiology
  • Rats


  • Calcium-Binding Proteins
  • Nerve Tissue Proteins
  • Parvalbumins
  • biocytin
  • Lysine