Effects of potassium channel blockers on synaptic plasticity in the corticostriatal pathway.
High-frequency stimulation (HFS) of the cerebral cortex or underlying white matter usually induces long-term depression (LTD) in the corticostriatal pathway. Long-term potentiation (LTP) has been described in striatal cells exposed to extracellular tetraethylammonium (TEA). The facilitating effect of TEA may be due to blockade of K+ channels in the postsynaptic neurone or alternatively to presynaptic effects on the release of neurotransmitters such as glutamate or dopamine. We compared the effects of HFS on LTP in striatal cells in four groups of neurones. HFS in control conditions induced LTD (-28.6 +/- 2.0% at 20 min, n = 10) whereas HFS in extracellular TEA (30 mM) induced LTP (+51.0 +/- 24.2% at 20 min, n = 7). LTP was not induced in cells loaded with intracellular Cs (-20.3 +/- 11.4% at 20 min, n = 10) or intracellular TEA (-11.8 +/- 8.9% at 20 min, n = 10), despite comparable effects on postsynaptic responses to HFS. Since the effects of the intracellular K+ channel blockers are limited to the cell being recorded from. these findings suggest that the facilitating effect of extracellular TEA on LTP induction involves a presynaptic action.
Department of Anatomy and Structural Biology, University of Otago, Dunedin, New Zealand.
J R
JR
Wickens
D
D
Mckenzie
E
E
Costanzo
G W
GW
Arbuthnott
D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology*; D002586:Cesium / Q000494:pharmacology; D003342:Corpus Striatum / Q000187:drug effects / Q000502:physiology*; D005110:Extracellular Space / Q000737:chemistry; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000737:chemistry; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008839:Microelectrodes; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D019789:Tetraethylammonium / Q000494:pharmacology
D026902:Potassium Channel Blockers; D015221:Potassium Channels; D002586:Cesium; D019789:Tetraethylammonium