Depolarization current signals

BK currents consisted of transient and steady-state components. The transient currents were abolished by ryanodine (10 fiM), indicating that they are activated by Ca2+ sparks. The lag from the onset of depolarization (activation of VDCCs) to the first transient BK current was around 50 ms. This delay is much too long to be attributed to local signalling from VDCCs to RyRs such as occurs in heart, and instead is consistent with the idea of loose coupling between VDCCs and RyRs (Fig. 1 A) (Collier et al 2000). Spark-activated transient BK currents remained in the presence of the VDCC antagonist diltiazem (50 //M). However, the frequency of... 

Adenosine receptors are found on myocytes in the atria and sinoatrial and A-V nodes. Stimulation of these receptors acts via a G-protein signaling cascade to open an acetylcholine-sensitive outward potassium current. This leads to hyperpolarization of the resting membrane potential, a decrease in the slope of phase 4 spontaneous depolarization, and shortening of the action potential duration. 

Helmut Haas and colleagues showed that, in hippocampal pyramidal neurons, H2-receptor stimulation potentiates excitatory signals by decreasing a Ca2+-activated K+ conductance, presumably via cAMP production [11], H2-receptor activation depolarizes thalamic relay neurons slightly, increasing markedly apparent membrane conductance, a response due to enhancement of the hyperpolarization-activated cation current lh [20],... 

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