title: Columnar distribution of activity dependent gabaergic depolarization in sensorimotor cortical neurons.
abstract: BACKGROUND
  GABA, the major inhibitory neurotransmitter in CNS, has been demonstrated to paradoxically produce excitation even in mature brain. However activity-dependent form of GABA excitation in cortical neurons has not been observed. Here we report that after an intense electrical stimulation adult cortical neurons displayed a transient GABA excitation that lasted for about 30s.
  
  
  RESULTS
  Whole-cell patch recordings were performed to evaluate the effects of briefly applied GABA on pyramidal neurons in adult rodent sensorimotor cortical slice before and after 1 s, 20 Hz suprathreshold electrical stimulation of the junction between layer 6 and the underlying white matter (L6/WM stimulation). Immediately after L6/WM stimulation, GABA puffs produced neuronal depolarization in the center of the column-shaped region. However, both prior to or 30s after stimulation GABA puffs produced hyperpolarization of neurons. 2-photon imaging in neurons infected with adenovirus carrying a chloride sensor Clomeleon revealed that GABA induced depolarization is due to an increase in [Cl-]i after stimulation. To reveal the spatial extent of excitatory action of GABA, isoguvacine, a GABAA receptors agonist, was applied right after stimulation while monitoring the intracellular Ca2+ concentration in pyramidal neurons. Isoguvacine induced an increase in [Ca2+]i in pyramidal neurons especially in the center of the column but not in the peripheral regions of the column. The global pattern of the Ca2+ signal showed a column-shaped distribution along the stimulation site.
  
  
  CONCLUSIONS
  These results demonstrate that the well-known inhibitory transmitter GABA rapidly switches from hyperpolarization to depolarization upon synaptic activity in adult somatosensory cortical neurons.
authors.affiliation: Department of Biomedical Engineering, University of North Carolina at Chapel Hill, CB#7575, Chapel Hill, NC, USA.
authors.forename: Jaekwang
authors.initials: J
authors.lastname: Lee
authors.forename: Junsung
authors.initials: J
authors.lastname: Woo
authors.forename: Oleg V
authors.initials: OV
authors.lastname: Favorov
authors.forename: Mark
authors.initials: M
authors.lastname: Tommerdahl
authors.forename: C Justin
authors.initials: CJ
authors.lastname: Lee
authors.forename: Barry L
authors.initials: BL
authors.lastname: Whitsel
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D004558:Electric Stimulation; D049452:Green Fluorescent Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000502:physiology*; D017966:Pyramidal Cells / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D059010:Single-Cell Analysis; D013003:Somatosensory Cortex / Q000502:physiology*; D013569:Synapses / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D002712:Chlorides; D049452:Green Fluorescent Proteins; D005680:gamma-Aminobutyric Acid; D002118:Calcium