Activation of overexpressed GIRK channels in cultured hippocampal neurons hyperpolarized the cell by 11-14 mV and inhibited action potential firing by increasing the threshold current 2- to 3-fold.
Overexpression of GIRK channels via adenovirus gene transfer in cultured hippocampal neurons inhibits neuronal excitability by hyperpolarizing the cell and increasing the threshold for action potential firing.
G protein-gated inward rectifier K+ channel subunits 1-4 (GIRK1-4) have been cloned from neuronal and atrial tissue and function as heterotetramers. To examine the inhibition of neuronal excitation by GIRKs, we overexpressed GIRKs in cultured hippocampal neurons from 18 day rat embryos, which normally lack or show low amounts of GIRK protein and currents. Adenoviral recombinants containing the cDNAs for GIRK1, GIRK2, GIRK4, and the serotonin 1A receptor were constructed. Typical GIRK currents could be activated by endogenous GABAB, serotonin 5-HT1A, and adenosine A1 receptors in neurons coinfected with GIRK1+2 or GIRK1+4. Under current clamp, GIRK activation increased the cell membrane conductance by 1- to 2-fold, hyperpolarized the cell by 11-14 mV, and inhibited action potential firing by increasing the threshold current for firing by 2- to 3-fold. These effects were not found in non- and mock-infected neurons, and were similar to the effects of muscarinic stimulation of native GIRK currents in atrial myocytes. Two inhibitory effects of GIRK activation, hyperpolarization and diminution of depolarizing pulses, were simulated from the experimental data. These inhibitory effects are physiologically important in the voltage range between the resting membrane potential and the potential where voltage-gated Na+ and K+ currents are activated; that is where GIRK currents are outward.
Ehrengruber et al. (Tue,) reported a other. Adenovirus-mediated overexpression of GIRK channels vs. Non-infected and mock-infected neurons was evaluated on Cell membrane hyperpolarization and threshold current for action potential firing. Activation of overexpressed GIRK channels in cultured hippocampal neurons hyperpolarized the cell by 11-14 mV and inhibited action potential firing by increasing the threshold current 2- to 3-fold.