Calcium channels activated by hydrogen peroxide mediate. Jul 16, 2003 betaadrenergic receptor stimulation with isoproterenol 1 m caused an acceleration of current activation and a shift of v12 by 7. These results indicate that the cssensitive hyperpolarizationactivated inward current is present in the longitudinal muscle cells of pregnant rat uterus. The hyperpolarizationactivated current ih and its role in pacemaking activity in rat hippocampal stratum oriensalveus interneurones was studied using wholecell and perforated patch. Dendritic hyperpolarizationactivated currents modify the. Blind patch electrodes used for currentclamp recordings were filled with a. Voltageclamp recordings revealed ih as a slowly activating, inward current, activated by hyperpolarizing steps holding potential, vh 40 mv 1 with a reversal potential close to 30 mv.
Nitric oxide can increase heart rate by stimulating the hyperpolarizationactivated inward current, i f. Abstracta hyperpolarizationactivated cation conductance contributes to the membrane properties of a variety of cell types. Hyperpolarizationactivated ih current in mouse vestibular. Dopamine and baclofen inhibit the hyperpolarization. A hyperpolarizationactivated inward current in human. Aug 17, 2000 calcium channels activated by hydrogen peroxide mediate abscisic acid signalling in guard cells. Propofol suppresses a hyperpolarizationactivated inward. The ionic current responsible for pacemaker activity of sinoatrial node cells and purkinje. Properties of a hyperpolarizationactivated cation current in.
Role of hyperpolarizationactivated currents for the. Role of hyperpolarizationactivated currents for the intrinsic. Properties of the hyperpolarizationactivated current if. As these biological factors change across development, the brain undergoes. Using perforatedpatch voltageclamp recording, a prominent hyperpolarizationactivated inward cation current i h has been identified in dissociat. Using perforatedpatch voltageclamp recording, a prominent hyperpolarization activated inward cation current i h has been identified in dissociat. Effects of cyclicgmp on hyperpolarizationactivated inward. Multiple effects of serotonin and acetylcholine on hyperpolarizationactivated inward current in locomotor activityrelated neurons in cfosegfp mice yue dai and larry m. Patch electrodes were connected to an epc10 amplifier heka.
A typical feature of sinoatrial sa node pacemaker cells is the presence of an ionic current that activates upon hyperpolarization. Jordan department of physiology, university of manitoba, winnipeg, manitoba, canada submitted 16 december 2009. Magnitude of the inward rectifier current i k1 in relation to the hyperpolarizationactivated inward current i f. This study demonstrates the presence of the hyperpolarizationactivated current i h in intrinsically photosensitive retinal ganglion cells. I f otherwise known as i h is widely distributed in the nervous system and plays a substantial role in determining. Activated during a phasic hyperpolarization, this mixed cation current.
In the thalamus, a prominent hyperpolarizationactivated cation conductance exists in thalamocortical cells, and this current is implicated in the neuromodulation of complex firing behaviors. Pdf hyperpolarizationactivated inward chloride current in. Hyperpolarizationactivated inward current in ventricular myocytes. Activation of a g proteincoupled inwardly rectifying k. Hyperpolarizationactivated inward current in ventricular. Voltageclamp recordings revealed ih as a slowly activating, inward current, activated by hyperpolarizing steps holding potential, vh 40 mv, with a reversal potential close to 30 mv.
Hyperpolarizationactivated current, in mathematical. Citeseerx document details isaac councill, lee giles, pradeep teregowda. Hyperpolarization is a change in membrane potential, neuroscientists measure it using a technique known as patch clamping. Hyperpolarizationactivated current, in mathematical models.
The voltagedependent hyperpolarizationactivated cyclic nucleotidegated hcn channels generate a hyperpolarizationactivated cation inward current, named ih for hyperpolarization activated current in neurons and if for funny current in cardiac cells. Modulation of the hyperpolarizationactivated current if by. Ramps were applied during active or inactive states of. Hyperpolarizationactivated inward current longduration sec step hyperpolarizations evoked inward currents from cellattached patches obtained from both the somatic and apical dendritic regions of hippocampal ca1 pyramidal neurons fig. Its activation curve ranged from n50 to 120 mv with a midactivation point of 84. A hyperpolarizationactivated cation current i h contributes to. The hyperpolarizationactivated current ih underlying inward rectification in neurons of the rats dorsal nucleus of the lateral lemniscus dnll was investigated using whole cell patch clamp techniques. In currentclamp configuration, injection of hyperpolarizing currents induced variations of membrane voltage with prominent timedependent rectification increasing with current amplitudes. The nerve excitability test in sma patients showed increased inward rectification in the current. The activation of i h in the central neurons was first noted in the hippocampal pyramidal cells.
External cs 1 suppresses the inwardrectifying effect of external k1. Nitric oxide can increase heart rate by stimulating the. Cation and voltage dependence of lidocaine inhibition of. The role of this hyperpolarizationactivated current, which is also known as the funny current or pacemaker current, in the spontaneous pacemaker activity of sa nodal cells remains a matter of intense debate. To characterize the hyperpolarizationactivated inward current ih and to. The hyperpolarizationactivated current ih and its role in pacemaking activity in rat hippocampal stratum oriensalveus interneurones was studied using wholecell and perforated patch clamp configurations. Zd7288 inhibited the hyperpolarization activated cationic current i f in. Ion channel, pacemaker current, patch clamp, human atrial myocyte. The cation conductance activated upon hyperpolarization of the membrane be. The i f current was studied in cells isolated enzymatically from the san region of adult c57bl6j mice. Typical hyperpolarizationactivated inward currents in calyx terminals. Hcurrent, also known as hyperpolarizationactivated current ih, is an inward current generated by the hyperpolarizationactivated cyclic nucleotidegated hcn cation channels. The role of the hyperpolarizationactivated current in modulating. Inhibitory actions of zeneca zd7288 on wholecell hyperpolarization activated inward current if in guineapig dissociated sinoatrial node cells.
Modulation of hyperpolarizationactivated inward current. High external k1 enhances the inward rectification of membrane potential, an effect mediated by a fast, hyperpolarization activated, inwardly rectifying potassium current kir. Cation current activated by hyperpolarization ih in. The presence of a hyperpolarizationactivated inward current ih was investigated in mouse vestibular primary neurons using the wholecell patchclamp technique. The conductance in 10 mm external cacl 2 was 22 ps fig. The hyperpolarizationactivated current ih underlying inward rectification in. High external k1 enhances the inward rectification of membrane potential, an effect mediated by a fast, hyperpolarizationactivated, inwardly rectifying potassium current kir.
Hyperpolarizing voltage steps evoke slowly activating inward currents in a variety of neurones and in cardiac cells. Journal of molecular and cellular cardiology 1992 24, 451455. The hyperpolarization activated current is not only expressed in pacemaker cells of the heart. Multiple effects of serotonin and acetylcholine on. It has been demonstrated that slowly activating inward currents are evoked by hyperpolarizing voltage steps in a variety of neurons, including pvn, area postrema,14 and dorsal root ganglion neurons. Molecular characterization of the hyperpolarization. Hyperpolarizationactivated current ih in ganglioncell. May 11, 2018 h current, also known as hyperpolarization activated current ih, is an inward current generated by the hyperpolarization activated cyclic nucleotidegated hcn cation channels. The observed current shares the basic characteristics of i h in other cell types, namely a slow, inwardlyrectifying current activated by membrane hyperpolarization. A hyperpolarization activated inward current in human myocardial cells. Ih peaked in 400 ms at 36 c, was fully activated at 100 mv, and did not inactivate during 10 s. A hyperpolarizationactivated inward current in human myocardial cells.
Oct 05, 2001 the hyperpolarization activated inward current i h is an inward current that is slowly activated by membrane hyperpolarization, and was first detected in the sinoatrial node cells. Ih plays an essential role in regulating neuronal properties, synaptic integration and plasticity, and synchronous activity in the brain. Hac4 is composed of 1150 amino acid residues, and its cytoplasmic n and cterminal regions are longer than those of hac. These inward currents were slowly activating, noninactivating, and slowly deactivating. The hyperpolarizationactivated current ih underlying inward rectification in neurons of the rats dorsal nucleus of the lateral lemniscus dnll was investigated using whole cell patchclamp techniques. Methods and resultsthe wholecell patchclamp technique was used to record if in isolated ventricular myocytes from 34 failing dilated dcm. In this study, we examine the relation between the pro. Ramps were applied during active or inactive states of the hyperpolarization activated current. We have investigated the properties of the hyperpolarizationactivated i f current in pacemaker cells from the mouse sinoatrial node san.
Using this method they are able to record ion currents passing through individual channels. An inward current ih was activated by hyperpolarization from. Read inward rectifying membrane currents activated by hyperpolarization in immature rat olfactory cortex neurones in vitro, brain research on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. This is done using a glass micropipette, also called a patch pipette, with a 1 micrometer diameter. Characterization of the hyperpolarizationactivated inward current in. The hyperpolarizationactivated current i h underlying inward rectification in neurons of the rats dorsal nucleus of the lateral lemniscus dnll was investigated using whole cell patch clamp techniques. Hcn channel trafficking along dendrites in the hippocampus of rats has shown that hcn channels are quickly shuttled to the surface in response to neural activity. The hyperpolarizationactivated inward current, ih, plays a key role in the generation of rhythmic activities in thalamocortical tc relay neurons. The wholecell variation of the patch clamp technique was employed to investigate the basic properties of i f. We have investigated the properties of the hyperpolarization activated i f current in pacemaker cells from the mouse sinoatrial node san. Hyperpolarizationactivated current i h in vestibular calyx.
Ih was associated with a conductance increase and reversed polarity at about 40 mv by extrapolation. The aim of present study is to investigate the effects of cgmp on hyperpolarization activated inward current i f, pacemaker current of the heart, in rabbit sinoatrial node cells using the wholecell patch clamp technique. Hyperpolarizationactivated inward current in neurons of the. The aim of this study was to investigate possible regulation of the hyperpolarizationactivated current i f by cytosolic calcium in guineapig sinoatrial sa node cells.
Cation and voltage dependence of lidocaine inhibition of the. Using patch clamp electrophysiology, we investigated inward i h activated by a hyperpolarization to. Using perforated patch voltageclamp recording, a prominent hyperpolarizationactivated inward cation current i h has been identified in dissociated, cultured and replated, superior cervical sympathetic scg neurones from 17dayold rats. A hyperpolarizationactivated, cyclic nucleotidegated, ih. Patch recordings were made from dnll neurons of young rats 2 days old in 400 micro. Pdf hyperpolarizationactivated inward chloride current. We cloned a cdna hac4 that encodes the hyperpolarizationactivated cation channel i f or i h by screening a rabbit sinoatrial sa node cdna library using a fragment of rat braini f cdna. External cs 1 suppresses the inward rectifying effect of external k1. Hyperpolarizationactivated inward current in neurons of the rats. The i h channels activate, with a slow time course, at hyperpolarizing voltages beyond. In the present work, we use the perforated patch and conventional whole cell clamp to demonstrate that inward rectification is due to the presence of a hyperpolarizationactivated, cyclic nucleotidegated, nonselective cationic current that exhibits many similarities with i h. Dopamine 30 microm reduced the amplitude of ih by 10. The effect on i f was further evaluated in rabbit isolated patch clamped sinoatrial node cells.
Longduration sec step hyperpolarizations evoked inward currents from cellattached patches obtained from both the somatic and apical dendritic regions of hippocampal ca1 pyramidal neurons fig. Hyperpolarizationactivated cyclic nucleotide gated hcn channels are integral membrane proteins that serve as nonselective voltagegated cation channels in the plasma membranes of heart and brain cells. The standard extracellular solution contained in mm. Modulation of the hyperpolarizationactivated current if. Hyperpolarizationactivated inward current in neurons of. Two kinetically distinct components of hyperpolarization. Hyperpolarizationactivated calcium channels at the tip of. The hyperpolarizationactivated inward current i h is an inward current that is slowly activated by membrane hyperpolarization, and was first detected in the sinoatrial node cells. A hyperpolarization activated inward current i f is. Sturgess cardiovascular research department, zeneca pharmaceuticals, macclesfield. Calcium channels activated by hydrogen peroxide mediate abscisic acid signalling in guard cells. The presence of a hyperpolarizationactivated inward current ih was investigated in mouse vestibular primary neurons using the wholecell patch clamp technique.
This study demonstrates the presence of the hyperpolarization activated current i h in intrinsically photosensitive retinal ganglion cells. Using wholecell patch clamp, we recorded from isolated calyx. Materials and methods wholecell recordings of hyperpolarization activated currents were performed in vpn using an isolation procedure described previously 5. Apr 28, 2017 using patch clamp electrophysiology, we investigated inward i h activated by a hyperpolarization to. Its activation curve ranged from approximately 50 to 120 mv with a midactivation point of 84. The steadystate activation curve for the hyperpolarizationactivated inward current in human myocytes extends from 60 to 120 mv with a halfmaximum potential around 95 mv. Read inwardrectifying membrane currents activated by hyperpolarization in immature rat olfactory cortex neurones in vitro, brain research on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Normallypolarized tissue from the human atrial myocardium usually exhibits a diastolic depolarization phase which can be suppressed reversibly by cs or enhanced by inhibiting the inward rectifier k current.
The aim of present study is to investigate the effects of cgmp on hyperpolarization activated inward current i f, pacemaker current of the heart, in rabbit sinoatrial node cells using the wholecell patch. Show full abstract 1 40% of the patches contained either voltageindependent a or hyperpolarization activated b, inward rectifying channels with short mean open times 16 msec for a, and 8. Properties of the hyperpolarizationactivated current if in. In most myenteric ah neurons but not s neurons, step hyperpolarizations from the resting potential evoked an inward current ih. Calcium influx through hyperpolarizationactivated cation. A hyperpolarizationactivated, cyclic nucleotidegated. Subsequently, the i h channel was found to be prevalent in the central neurons. The role of the hyperpolarizationactivated inward current. Its effects have been studied in single, freshly dissociated guinea. Hcn channels are thought to consist of four either identical or nonidentical subunits that are integrally embedded in the cell membrane to create an ionconducting pore. Celltype specific development of the hyperpolarization.
Magnitude of the inward rectifier current i k1 in relation to the hyperpolarization activated inward current i f. The channels p ca p cl ratio deduced from current reversal potential fig. The hyperpolarizationactivated inward current if has been discussed to. The hyperpolarizationactivated inward current, ih, plays a key role in the. Properties of a hyperpolarizationactivated cation current. Show full abstract 1 40% of the patches contained either voltageindependent a or hyperpolarizationactivated b, inwardrectifying channels with short mean open times 16 msec for a, and 8. Patch recordings were made from dnll neurons of young rats 2 days old in 400. Characterization of a hyperpolarizationactivated inward current in. Effects of cyclicgmp on hyperpolarizationactivated.