title: Subthreshold oscillation of the membrane potential in magnocellular neurones of the rat supraoptic nucleus.
abstract: Electrophysiological properties and ionic basis of subthreshold oscillation of the membrane potential were examined in 104 magnocellular neurones of the rat supraoptic nucleus using intracellular recording techniques in a brain slice preparation. Subthreshold oscillation of the membrane potential occurring in all neurones examined was voltage dependent. Oscillation was initiated 7-12 mV negative to the threshold of fast action potentials. Oscillation was the result of neither excitatory nor inhibitory synaptic activity nor of electric coupling. Frequency analyses revealed a broad band frequency distribution of subthreshold oscillation waves (range 10-70 Hz). The frequency band of 15-33 Hz was observed in neurones depolarized close to the threshold of discharge. Subthreshold oscillation was blocked by TTX (1.25-2.5 microM) as well as by TEA (15 mM). Subthreshold oscillation was not blocked by low Ca(2+)-high Mg(2+) superfusate, CdCl(2), TEA (1-4.5 mM), 4-aminopyridine, apamin, charybdotoxin, iberiotoxin, BaCl(2), carbachol and CsCl. During application of TTX, stronger depolarization induced high-threshold oscillation of the membrane potential at a threshold of about -32 mV. These oscillation waves occurred at a mean frequency of about 35 Hz and were blocked by CdCl(2). Effects of ion channel antagonists suggest that subthreshold oscillation is generated by the interaction of a subthreshold sodium current and a subthreshold potassium current. The generation of high-threshold oscillation during TTX involves a high-threshold calcium current. Subthreshold oscillation of the membrane potential may be important for the inter-neuronal synchronization of discharge and for the amplification of synaptic events.
authors.affiliation: Department of Physiology and Pathophysiology, Johannes Gutenberg-University, Saarstrasse 21, D-55099 Mainz, Germany. boehmer@mail.uni-mainz.de
authors.forename: G
authors.initials: G
authors.lastname: Boehmer
authors.forename: W
authors.initials: W
authors.lastname: Greffrath
authors.forename: E
authors.initials: E
authors.lastname: Martin
authors.forename: S
authors.initials: S
authors.lastname: Hermann
mesh_terms: D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology*; D002104:Cadmium / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D019850:Heptanol / Q000494:pharmacology; D066298:In Vitro Techniques; D008274:Magnesium / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009991:Oscillometry; D026902:Potassium Channel Blockers; D011343:Procaine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013495:Supraoptic Nucleus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D019789:Tetraethylammonium / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D000779:Anesthetics, Local; D018679:Cholinergic Agonists; D026902:Potassium Channel Blockers; D002104:Cadmium; D013779:Tetrodotoxin; D011343:Procaine; D019789:Tetraethylammonium; D019850:Heptanol; D008274:Magnesium; D002118:Calcium