Hippocampal Pyramidal Neurons Comprise Two Distinct Cell Types that Are Countermodulated by Metabotropic Receptors

Graves, AR. Moore, SJ. Bloss, EB, Mensh, BD. Kath, WL. Spruston, N. (2012) Hippocampal Pyramidal Neurons Comprise Two Distinct Cell Types that Are Countermodulated by Metabotropic Receptors. Neuron 76: 776-789.

Two pyramidal cell types? "our results support a model of hippocampal processing in which the two pyramidal cell types are predominantly segregated into two parallel pathways that process distinct modalities of information"

rat hippocampal slices. supratheshold step current evoked one of two patterns: regular spiking or bursting. Extracted several (30ish) features and clustered them. Only two clusters came out of analysis.

The bursting class has a more extensive tuft, whereas regular-spiking cells have more extensive basal dendrites.

They made EPSC-like current injections. All neurons responded with a mixture of single-spikes and bursts. But cells still distinguishable from temporal pattern of bursting. Regular spiking neurons responded at first with single spikes early and bursts later. Bursting neurons fired bursts early and single spikes later.

Burstiness can be modulated based on activity - theta-burst stimulation can make both cell types more bursty. This burst plasticity can be modulated by glutamate and acytelocholine antagonists. Burst plasticity does not interconvert one cell type to the other. Thus there are two stable cell type pathways out of CA1.

So there's a seperate spatial and non-spatial loop that doesn't go through DG. And the tri-synpatic pathway through DG that combines the info. The two types are separated - CA1p has more of the late bursting cells (with larger basal trees), and CA1d has more early bursting cells.