Origin of post-depolarization hyperpolarizations in a grease-gap recording preparation.
In grease-gap recording preparations, depolarizing responses evoked by agonists are often followed by a hyperpolarization (post-depolarization hyperpolarization). We have investigated the origin of these post-depolarization hyperpolarizations in the rat CA1-subiculum slice. They were evoked by L-glutamate, N-methyl-d-aspartate or alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate in approximately 80% of the slices tested. The post-depolarization hyperpolarizations evoked by perfusion of N-methyl-d-aspartate through the CA1 compartment of the chamber, persisted when N-methyl-d-aspartate receptors in the subicular compartment were blocked with D-2-amino-5-phosphonopentanoate. Carbachol only blocked the post-depolarization hyperpolarizations evoked by alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate at concentrations which also blocked the depolarization. The post-depolarization hyperpolarization was selectively blocked by perfusion with Ca(2+)-free medium and by administration of ouabain, and showed a marked sensitivity to temperature. It is concluded that the post-depolarization hyperpolarizations observed in this preparation are not a consequence of diffusion of the agonist through the slice. The evidence is, however, consistent with them being generated by activation of the electrogenic Na(+)-K+ pump, although we cannot exclude an additional contribution from Ca(2+)- or voltage-dependent K+ currents.
Fanning
G R
GR
Department of Biomedical Sciences, Marischal College, University of Aberdeen, United Kingdom.
Ganesalingam
N
N
Davies
S N
SN
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D005071:Evoked Potentials / Q000187:drug effects; D005260:Female; D018698:Glutamic Acid / Q000494:pharmacology*; D006624:Hippocampus / Q000187:drug effects* / Q000378:metabolism; D066298:In Vitro Techniques; D016202:N-Methylaspartate / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects / Q000378:metabolism; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology*
D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D016202:N-Methylaspartate; D015763:2-Amino-5-phosphonovalerate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D000254:Sodium-Potassium-Exchanging ATPase