Lack of Regulation by Intracellular Ca2+ of the Hyper Polarization‐Activated Cation Current in Rat Thalamic Neurones
Open Access
- 1 August 1997
- journal article
- research article
- Published by Wiley in The Journal of Physiology
- Vol. 503 (1), 79-85
- https://doi.org/10.1111/j.1469-7793.1997.079bi.x
Abstract
1. The regulation of the hyperpolarization-activated cation current, Ih, in thalamocortical neurones by intracellular calcium ions has been implemented in a number of mathematical models on the waxing and waning behaviour of synchronized rhythmic activity in thalamocortical circuits. In the present study, the Ca2+ dependence of Ih in thalamocortical neurones was experimentally investigated by combining Ca2+ imaging and patch-clamp techniques in the ventrobasal thalamic complex (VB) in vitro. 2. Properties of Ih were analysed before and during rhythmic stimulation of Ca2+ entry by trains of depolarizing voltage pulses. Despite a significant increase in intracellular Ca2+ concentration ([Ca2+]i) from resting levels of 74 +/- 23 nM to 251 +/- 78 nM upon rhythmic stimulation, significant differences in the voltage dependence of Ih activation did not occur (half-maximal activation at -86.4 +/- 1.3 mV vs. -85.2 +/- 2.9 mV; slope of the activation curve, 11.2 +/- 2.4 mV vs. 12.5 +/- 2.5 mV). Recording of Ih with predefined values of [Ca2+]i (13.2 nM or 10.01 microM in the patch pipette) revealed no significant differences in the activation curve or the fully activated I-V relationship of Ih. 3. In comparison, stimulation of the intracellular cyclic adenosine monophosphate (cAMP) pathway induced a significantly positive shift in Ih voltage dependence of +5.1 +/- 1.9 mV, with no alteration in the fully activated I-V relationship. 4. These data argue against a direct regulation of Ih by intracellular Ca2+, and particularly do not support a primary role of Ca(2+)-dependent modulation of the Ih channels in the waxing and waning of sleep spindle oscillations in thalamocortical neurones.Keywords
This publication has 29 references indexed in Scilit:
- SLEEP AND AROUSAL: Thalamocortical MechanismsAnnual Review of Neuroscience, 1997
- Control of Spatiotemporal Coherence of a Thalamic Oscillation by Corticothalamic FeedbackScience, 1996
- Queer Current and Pacemaker: The Hyperpolarization-Activated Cation Current in NeuronsAnnual Review of Physiology, 1996
- What Stops Synchronized Thalamocortical Oscillations?Neuron, 1996
- Specific bradycardic agents block the hyperpolarization-activated cation current in central neuronsNeuroscience, 1994
- Practical Aspects of Measuring [Ca2+] with Fluorescent IndicatorsMethods in cell biology, 1994
- A Practical Guide to the Preparation of Ca2+ BuffersMethods in cell biology, 1994
- Thalamocortical Oscillations in the Sleeping and Aroused BrainScience, 1993
- Effects of intracellular calcium chelation on voltage-dependent and calcium-dependent currents in cat neocortical neuronsNeuroscience, 1992
- Intracellular calcium does not directly modulate cardiac pacemaker (if) channelsPflügers Archiv - European Journal of Physiology, 1991