title: Properties of the hyperpolarization-activated current in rat hippocampal CA1 pyramidal cells.
abstract: 1. Voltage and current clamp recordings were performed on CA1 rat hippocampal pyramidal cells using the patch clamp technique on "in vitro" slice preparations. 2. Hyperpolarizations from a holding potential of -35 mV elicited activation of the hyperpolarization-activated current (Ih) starting at voltages near -50 mV. 3. Ih recorded in voltage clamp conditions was blocked by external caesium (5 mM). 4. Raising the external K concentration from 4.35 to 24.35 mM sensibly increased the slope of the current-voltage (I/V) curve. Decreasing the external Na concentration from 133.5 to 33.5 mM depressed Ih without grossly altering the I/V slope. 5. The Ih fully activated I/V relation measured in the range -140 to -45 mV was linear with an extrapolated reversal at -17.0 +/- -1.6 (SE) mV. The current activation curve comprised the range between about -50 and -140 mV with a half-maximal activation at about -98 mV. 6. Perfusion of unclamped neurons with Cs (2 mM) hyperpolarized their resting potential by 3.8 +/- 0.2 mV and decreased the membrane conductance, as expected if Ih were activated at rest. Firing caused by depolarizing current steps was prevented by Cs-induced hyperpolarization, and could be restored by returning the membrane voltage to resting level by constant current injection. 7. The Cd-insensitive (medium-duration) afterhyperpolarization (AHP) elicited by a train of action potentials at -60 mV had an amplitude of 3.9 +/- 0.3 mV and was nearly fully abolished by 2 mM Cs (82.7 +/- 7.4%). Cs removed the depolarizing part of the afterhyperpolarization as expected if Ih activation was responsible for this phase.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Dipartimento di Fisiologia e Biochimica Generali, Università di Milano, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Maccaferri
authors.forename: M
authors.initials: M
authors.lastname: Mangoni
authors.forename: A
authors.initials: A
authors.lastname: Lazzari
authors.forename: D
authors.initials: D
authors.lastname: DiFrancesco
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D002217:Carbachol / Q000494:pharmacology; D002586:Cesium / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology; D011712:Pyramidal Tracts / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D015222:Sodium Channels / Q000502:physiology
chemical_list: D007473:Ion Channels; D015221:Potassium Channels; D015222:Sodium Channels; D002104:Cadmium; D002586:Cesium; D002217:Carbachol; D002118:Calcium