UNASSIGNED: The hippocampus plays a key role in learning and memory. Previous studies suggested that the main types of principal neurons, dentate gyrus granule cells, @entity1251 pyramidal neurons, and @entity1249 pyramidal neurons, differ in their activity pattern, with sparse firing in granule cells and more frequent firing in @entity1251 and @entity1249 pyramidal neurons. It has been assumed but never shown that such different activity may be caused by differential synaptic excitation. To test this hypothesis, we performed high-resolution whole-cell patch-clamp recordings in anesthetized @entity35 in vivo. In contrast to previous in vitro data, both @entity1251 and @entity1249 pyramidal neurons fired action potentials spontaneously, with a frequency of    3-6 Hz, whereas granule cells were silent. Furthermore, both @entity1251 and @entity1249 cells primarily fired in bursts. To determine the underlying mechanisms, we quantitatively assessed the frequency of spontaneous excitatory synaptic input, the passive membrane properties, and the active membrane characteristics. Surprisingly, granule cells showed comparable synaptic excitation to @entity1251 and @entity1249 cells and the highest ratio of excitation versus hyperpolarizing inhibition. Thus, differential synaptic excitation is not responsible for differences in firing. Moreover, the three types of hippocampal neurons markedly differed in their passive properties. While granule cells showed the most negative membrane potential, @entity1251 pyramidal neurons had the highest input resistance and the slowest membrane time constant. The three types of neuron also differed in the active membrane characteristics. Granule cells showed the highest action potential threshold, but displayed the largest gain of the input-output curves. In conclusion, our results reveal that differential firing of the three main types of hippocampal principal neurons in vivo is not primarily caused by differences in the characteristics of the synaptic input, but by the distinct properties of synaptic integration and input-output transformation. This article is protected by copyright. All rights reserved.

Intrinsic membrane properties determine hippocampal differential firing pattern in vivo in anesthetized XXXX .

@entity35 :: ('10116', 'Species') :: ['rats'] @entity1251 :: ('54232(Tax:10116)', 'Gene') :: ['CA3'] @entity1249 :: ('310218(Tax:10116)', 'Gene') :: ['CA1']
@entity35 :: (10116,Species) :: ['rats']
