Theta-frequency bursting and resonance in cerebellar granule cells: experimental evidence and modeling of a slow k+-dependent mechanism.
Neurons process information in a highly nonlinear manner, generating oscillations, bursting, and resonance, enhancing responsiveness at preferential frequencies. It has been proposed that slow repolarizing currents could be responsible for both oscillation/burst termination and for high-pass filtering that causes resonance (Hutcheon and Yarom, 2000). However, different mechanisms, including electrotonic effects (Mainen and Sejinowski, 1996), the expression of resurgent currents (Raman and Bean, 1997), and network feedback, may also be important. In this study we report theta-frequency (3-12 Hz) bursting and resonance in rat cerebellar granule cells and show that these neurons express a previously unidentified slow repolarizing K(+) current (I(K-slow)). Our experimental and modeling results indicate that I(K-slow) was necessary for both bursting and resonance. A persistent (and potentially a resurgent) Na(+) current exerted complex amplifying actions on bursting and resonance, whereas electrotonic effects were excluded by the compact structure of the granule cell. Theta-frequency bursting and resonance in granule cells may play an important role in determining synchronization, rhythmicity, and learning in the cerebellum.
D'Angelo
E
E
Department of Molecular/Cellular Physiology and Instituto Nazionale per la Fisica della Materia, University of Pavia, I-27100 Pavia, Italy. dangelo@unipv.it
Nieus
T
T
Maffei
A
A
Armano
S
S
Rossi
P
P
Taglietti
V
V
Fontana
A
A
Naldi
G
G
D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D003594:Cytoplasmic Granules; D004558:Electric Stimulation; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008959:Models, Neurological; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D009532:Nickel / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000378:metabolism*; D051381:Rats; D012964:Sodium / Q000378:metabolism; D019789:Tetraethylammonium; D013779:Tetrodotoxin / Q000494:pharmacology; D013826:Theta Rhythm
D026902:Potassium Channel Blockers; D015221:Potassium Channels; D013779:Tetrodotoxin; D019789:Tetraethylammonium; D009532:Nickel; D012964:Sodium; D015761:4-Aminopyridine; D011188:Potassium; D002118:Calcium