Mapping the electrophysiological and morphological properties of CA1 pyramidal neurons along the longitudinal hippocampal axis.
Differences in behavioral roles, anatomical connectivity, and gene expression patterns in the dorsal, intermediate, and ventral regions of the hippocampus are well characterized. Relatively fewer studies have, however, focused on comparing the physiological properties of neurons located at different dorsoventral extents of the hippocampus. Recently, we reported that dorsal CA1 neurons are less excitable than ventral neurons. There is little or no information for how neurons in the intermediate hippocampus compare to those from the dorsal and ventral ends. Also, it is not known whether the transition of properties along the dorsoventral axis is gradual or segmented. In this study, we developed a statistical model to predict the dorsoventral position of transverse hippocampal slices. Using current clamp recordings combined with this model, we found that CA1 neurons in dorsal, intermediate, and ventral hippocampus have distinct electrophysiological and morphological properties and that the transition in most (but not all) of these properties from the ventral to dorsal end is gradual. Using linear and segmented regression analyses, we found that input resistance and resting membrane potential changed linearly along the V-D axis. Interestingly, the transition in resonance frequency, rebound slope, dendritic branching in stratum radiatum, and action potential properties was segmented along the V-D axis. Together, the findings from this study highlight the heterogeneity in CA1 neuronal properties along the entire longitudinal axis of hippocampus.
Center for Learning and Memory, University of Texas at Austin, Austin, Texas.
Ruchi
R
Malik
Center for Learning and Memory, University of Texas at Austin, Austin, Texas.|Department of Biology, Rhodes College, Memphis, Tennessee.
Kelly Ann
KA
Dougherty
Center for Learning and Memory, University of Texas at Austin, Austin, Texas.
Komal
K
Parikh
Center for Learning and Memory, University of Texas at Austin, Austin, Texas.
Connor
C
Byrne
Center for Learning and Memory, University of Texas at Austin, Austin, Texas.
Daniel
D
Johnston
D000818:Animals; D055592:Biophysical Phenomena / Q000502:physiology; D001703:Biophysics; D001931:Brain Mapping; D056547:CA1 Region, Hippocampal / Q000166:cytology*; D003712:Dendrites / Q000502:physiology; D004558:Electric Stimulation; D018683:Excitatory Amino Acid Agents / Q000494:pharmacology; D066298:In Vitro Techniques; D016014:Linear Models; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D008959:Models, Neurological; D009415:Nerve Net / Q000166:cytology / Q000502:physiology*; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018709:Statistics, Nonparametric
D018683:Excitatory Amino Acid Agents
dendritic branching; dorsal hippocampus; firing output; intermediate hippocampus; intrinsic excitability; resonance frequency; ventral hippocampus