Depolarization-induced facilitation of a plateau-generating current in ventral horn neurons in the turtle spinal cord.
Plasticity at the neuronal level commonly involves use-dependent changes in strength of particular synaptic pathways or regulation of postsynaptic properties by modulatory transmitters. Here we analyze a novel form of short-term plasticity mediated by use-dependent facilitation of postsynaptic responsiveness. Using current- and voltage-clamp recordings, we found that all spinal ventral horn neurons able to generate plateau potentials showed depolarization-induced facilitation of the underlying inward current. Facilitation was noticeable when the neurons were depolarized to more than -50 mV at intervals <4 s. When stimulation with fast triangular voltage ramps was used, the inward current activated at a less depolarized potential during the second ramp. The inward current and facilitation was eliminated by nifedipine, a selective antagonist of L-type calcium channels. Depolarization-induced facilitation of low-voltage-activated L-type calcium channels is suggested to be the underlying mechanism. It is noted that facilitation occurs on a time scale compatible with a role in phasic motor activity.
Svirskis
G
G
Laboratory of Neurophysiology, Biomedical Research Institute, Kaunas Medical Academy, Lithuania.
Hounsgaard
J
J
D000818:Animals; D000870:Anterior Horn Cells / Q000187:drug effects / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004594:Electrophysiology; D066298:In Vitro Techniques; D007395:Interneurons / Q000187:drug effects / Q000378:metabolism; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology; D009046:Motor Neurons / Q000187:drug effects; D009116:Muscarine / Q000494:pharmacology; D018721:Muscarinic Agonists / Q000494:pharmacology; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009473:Neuronal Plasticity / Q000187:drug effects; D018408:Patch-Clamp Techniques; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D014426:Turtles / Q000502:physiology*
D002121:Calcium Channel Blockers; D007473:Ion Channels; D018721:Muscarinic Agonists; D018727:Muscarinic Antagonists; D009116:Muscarine