Spikelet currents in frog tectal neurons with different firing patterns in vitro.
Neuronal potential-dependent membrane currents are important in shaping the integration of synaptic inputs. Our recordings in voltage-clamp mode indicate that the small fast inward currents (spikelet currents), which were several times smaller than action potential (AP) currents, are a distinguished feature of 33% of neurons from 8 to 6 layers of the frog tectum. Out of all neuronal types described previously, only phasic cells and neurons with 'sag' in response to hyperpolarizing step current injection did not show spikelet currents. These small fast inward currents were sensitive to the intracellular administration of the sodium channel blocker QX-314, but not to the extracellular application of a glutamate receptor antagonist kynurenic acid. This suggests that spikelet currents are mediated by fast voltage-dependent Na(+) channels. Since spikelet currents could also be elicited with synaptic stimulation it is possible that spikelets are generated in dendrites and, thus, are important for fast integration of visual signals in tectal neurons.
Gutmaniene
Nijole
N
Laboratory of Neurophysiology, Institute for Biomedical Research, Kaunas University of Medicine, 4 Eiveniu Street, LT-50009 Kaunas, Lithuania.
Svirskiene
Natasa
N
Svirskis
Gytis
G
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D003712:Dendrites / Q000502:physiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011896:Rana temporaria / Q000033:anatomy & histology / Q000502:physiology*; D017470:Receptors, Glutamate / Q000187:drug effects / Q000378:metabolism; D026941:Sodium Channel Blockers / Q000494:pharmacology; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism; D013477:Superior Colliculi / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D014795:Visual Pathways / Q000187:drug effects / Q000502:physiology; D014796:Visual Perception / Q000187:drug effects / Q000502:physiology
D018691:Excitatory Amino Acid Antagonists; D017470:Receptors, Glutamate; D026941:Sodium Channel Blockers; D015222:Sodium Channels