Cyclic nucleotides directly enhance the opening of the tetrameric CNG and HCN channels, although the mechanism remains unclear. We examined why HCN and certain CNG subunits form functional homomeric channels, whereas other CNG subunits only function in heteromeric channels. The "defect" in the CNGA4 subunit that prevents its homomeric expression was localized to its C-linker, which connects the...

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels underlie the control of rhythmic activity in cardiac and neuronal pacemaker cells. In HCN, the polarity of voltage dependence is uniquely reversed. Intracellular cyclic adenosine monophosphate (cAMP) levels tune the voltage response, enabling sympathetic nerve stimulation to increase the heart rate. We present cryo-electron micr...

1,2,2-Tricyanoethanes, Elimination of HCN The elimination of HCN from 9-dicyanomethyl-fluorene (2), 1,1-diphenyl-1,2,2tricyanoethane (3), and 2-phenyl-I,l,2-tricyano-propane (4) in anhydrous methanol has been studied and shown to occur via an (E l)anion mechanism. Elimination of HCN from 2 in acidic, buffered and MeO~/MeOH solutions have also been studied. Addition of water or benzene to the re...

The apical tuft is the most remote area of the dendritic tree of neocortical pyramidal neurons. Despite its distal location, the apical dendritic tuft of layer 5 pyramidal neurons receives substantial excitatory synaptic drive and actively processes corticocortical input during behavior. The properties of the voltage-activated ion channels that regulate synaptic integration in tuft dendrites ha...

25 Hyperpolarization-activated, cyclic-nucleotide gated, non-specific cation (HCN) 26 channels have a well-characterized role in regulation of cellular excitability and network 27 activity. The role of these channels in control of epileptiform discharges is less 28 thoroughly understood. This is especially pertinent given altered HCN channel 29 expression in epilepsy. We hypothesized that inhib...

Background—The pacemaker current If is present in atrial and ventricular myocytes. However, it remains controversial whether If overexpression in diseased states might play a role for arrhythmogenesis, because first If activation in whole-cell recordings hardly overlapped the diastolic voltage of working myocardium. Methods and Results—To obtain further insight into IHCN and If properties, we p...

Part of the sympathetic flight-or-fight response is an increase in intracellular cyclic AMP (cAMP) that raises the rate of action potential generation in the heart pacemaker, the sinoatrial (SA) node (Robinson and Siegelbaum, 2003). The increased firing rate in the SA node increases the heart rate and cardiac output necessary to deliver more oxygen and nutrients to the muscles for the flight-or...

457 C o m m e n t a r y Ion channels are highly specialized to respond to a wide range of environmental stimuli, including transmem-brane voltage and chemical ligands (Hille, 2001). The response of channels to external cues causes a change in their ion conduction, which, in turn, modifies the behavior of excitable and nonexcitable cells. The hyper-polarization-activated and cyclic nucleotide–mo...

We have observed four carbon stars (W Ori, RW LMi [CIT6], Y CVn, and LP And [IRC+40540]) in the HCN(J = 1 → 0) line and three of them (RW LMi, Y CVn, and LP And) also in the CN(N = 1 → 0) line using the IRAM interferometer on Plateau de Bure. The HCN brightness distributions are centred on the stellar positions suggesting a photospheric origin of this molecule. We see the expected structure of ...

Output properties of neurons are greatly shaped by voltage-gated ion channels, whose biophysical properties and localization within axodendritic compartments serve to significantly transform the original input. The hyperpolarization-activated current, I(h), is mediated by hyperpolarization-activated cyclic nucleotide-gated (HCN) channels and plays a fundamental role in influencing neuronal exci...