[Abstract Title]. - Society for Neuroscience

Topic: B.10.b. Modulation of neuronal firing properties
Support: NINDS Grant 5F31NS055516
Title: Cell-type specific maintenance of neocortical firing type by network activity
Authors: *M. N. MILLER, S. B. NELSON;
Biol., Brandeis Univ., Waltham, MA
Abstract: The adult neocortical microcircuit is composed of multiple discrete cell-types that
differ morphologically, physiologically, and transcriptionally, and these cell-type-specific
properties permit distinct functional roles within the network. Maturation and maintenance of
cell-type specificity is most likely regulated by a complex interaction between genetic and
environmental factors, but the relative contributions of these have not been directly examined.
We combined genetic and anatomical labeling of cortical cell-types with chronic local muscimol
delivery in adult mice in vivo to ask whether cortical network activity is necessary for the
maintenance of cell-type specificity. 48 hours of local network inactivation increased the
excitability of fast-spiking interneurons (FS) and reduced the excitability of intratelencephalic
corticostriatal pyramidal cells (IT), but had no effect on their respective characteristic firing
types. In contrast, pyramidal-tract projecting pyramidal cells (PT), which under control
conditions exhibit spike-frequency acceleration in response to current injection, either lost
acceleration to become non-adapting or, in the majority of cases, exhibited spike-frequency
adaptation accompanied by a dramatic increase in input resistance. The combination of spikefrequency
adaptation and high input resistance is reminiscent of both IT pyramidal cells and
immature PT pyramidal cells, suggesting that PT physiological properties quickly regress to an
immature and less-differentiated state if not actively maintained by network activity.
Furthermore, the effect of chronic activity blockade on PT but not IT or FS populations indicates
that activity-dependent maintenance of neuronal phenotype is cell-type specific.
Disclosures: M.N. Miller , None; S.B. Nelson, None.
Poster
240. Intrinsic Membrane Properties: Modulation of Neuronal Firing Properties by Inputs
and Activity
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 240.19/F1
Topic: B.10.c. Activity-dependent plasticity of intrinsic membrane properties
Support: Neuroinformatics Doctoral Training Centre Grant (EPSRC)