[The electrophysiological properties of voltage-gated potassium channels on cultivated porcine retinal ganglion cells irradiated with continuous near-infrared laser]

OBJECTIVE

To investigate the influence of continuous near-infrared (CNI) laser to potassium ion channels on retinal ganglion cell (RGC).

METHODS

Experiment study. Porcine RGC was cultured with enzymatic digestion method in vitro by taking off the retina from the piglets. Whole-cell patch clamp mode recordings were obtained from primary cultured porcine RGC. Whole-cell currents of porcine RGC irradiated with a single-mode CNI laser of 845 nm wavelength and 30 mW power were also recorded. The primary cultured porcine RGC were divided into laser irradiation group and control group according to whether they accepted CNI laser of 845 nm wavelength. t test was used to analyze the average peak amplitude between the two groups.

RESULTS

The cells had the morphological characteristics of typical neurons after one week cultured observed by inverted phase contrast microscope. The body and bumps with yellow-green fluorescence was positive cell which observed by immune cell fluorescence chemical testing. CNI laser had a regulation on outward potassium current of porcine RGC in a voltage-dependent manner. There was significant difference on the average peak amplitude of potassium current between the laser irradiation group [(634.4 ± 86.8) Pa] and the control group [(580.5 ± 116.4) Pa], respectively (n = 30, t = 7.923, P = 0.000).

CONCLUSIONS

CNI laser can change the properties of outward K(+) channel. Therefore, formation and releasing of action potential is affected. Further, physiological functions of RGC are regulated, which might contribute to the protection and restoration of injured RGC. It can be provided a new scholar direction for the protection of the RGC, which are injured by glaucoma.

A-type voltage-gated K+ currents influence firing properties of isolectin B4-positive but not isolectin B4-negative primary sensory neurons

Voltage-gated K+ channels (Kv) in primary sensory neurons are important for regulation of neuronal excitability. The dorsal root ganglion (DRG) neurons are heterogeneous, and the types of native Kv currents in different groups of nociceptive DRG neurons are not fully known. In this study, we determined the difference in the A-type Kv current and its influence on the firing properties between isolectin B4 (IB4)-positive and -negative DRG neurons. Whole cell voltage- and current-clamp recordings were performed on acutely dissociated small DRG neurons of rats. The total Kv current density was significantly higher in IB+-positive than that in IB(4)-negative neurons. Also, 4-aminopyridine (4-AP) produced a significantly greater reduction in Kv currents in IB4-positive than in IB4-negative neurons. In contrast, IB4-negative neurons exhibited a larger proportion of tetraethylammonium-sensitive Kv currents. Furthermore, IB4-positive neurons showed a longer latency of firing and required a significantly larger amount of current injection to evoke action potentials. 4-AP significantly decreased the latency of firing and increased the firing frequency in IB4-positive but not in IB4-negative neurons. Additionally, IB4-positive neurons are immunoreactive to Kv1.4 but not to Kv1.1 and Kv1.2 subunits. Collectively, this study provides new information that 4-AP-sensitive A-type Kv currents are mainly present in IB4-positive DRG neurons and preferentially dampen the initiation of action potentials of this subpopulation of nociceptors. The difference in the density of A-type Kv currents contributes to the distinct electrophysiological properties of IB4-positive and -negative DRG neurons.

Evidence of electroconformational changes in membrane proteins: field-induced reductions in intra membrane nonlinear charge movement currents

Experimental results are presented to show that a pulsed, intensive membrane potential can reduce intra membrane, nonlinear charge movement currents, which are the voltage-sensors in the voltage-dependent membrane proteins and in the excitation-contraction coupling of skeletal muscle fibers. The results indicate a possible mechanism involved in electrical injury: dysfunctions of the voltage-dependent membrane proteins caused by electroconformational damages in their voltage-sensors.

[Influence of He-Ne laser irradiation and local anesthetics on potassium channels in the snail neurons]

Using clamp method it had been shown that He-Ne laser irradiation of the snail neurons increases the amplitude of voltage-gated slow potassium currents in dose of 0.7 x 10(-4) (fluence 1.5 x 10(2) Wt/m2) and decreases it in dose 0.7 x 10(-3). Bupivacaine and lidocaine suppressed potassium currents. Laser irradiation in dose 0.7 x 10(-3) enhanced the inhibitory effect of bupivacaine (10 mcM) and in dose 0.7 x 10(-4) it decreased the inhibitory effect of bupivacaine. The results of the study suggest mechanisms of the He-Ne laser irradiation effect in combination with pharmacological substances on ion channels of electrically excitable cells.

Can electromagnetic radiations induce changes in the kinetics of voltage-dependent ion channels?

Ion channels are protein molecules, which can assume distinct open and closed conformational states, a phenomenon termed ion channel kinetics. The transitions from one state to another depend on the potential energy barrier that separates those two states. Therefore, it is rational to suppose that electromagnetic waves could interact with this barrier and induce changes in the rate transitions of this kinetic process. Our aim is to answer the question: can electromagnetic radiations induce changes in the kinetics of voltage-dependent ion channels? We simulated the effects of the low and high frequency electromagnetic waves on the sodium and potassium channels of the giant axon of Loligo. The key parameter measured was the fractional open time (fv), because it reflects the voltage dependence of the kinetics of channels. The electromagnetic radiations induced the following changes in the kinetics of the potassium and sodium channels: i/ low frequency waves kept the potassium channel 50% of the time open independent on the mean voltage applied through the membrane; ii/ a gradual inhibition of the inactivation on the sodium channel, when the amplitudes of the low frequency waves were increased; iii/ high frequency waves on the potassium channel, decreased both Vo (voltage in which the channel stays 50% open) and the steepness of fv (d fv/dV) as the amplitudes of the waves increased, and iv/ high frequency and low amplitude radiations on the sodium channel decreased the maximum value of fv (in relation to control), while high amplitudes increased this value. In conclusion, high and low frequency electromagnetic radiations were able to change the kinetics of the potassium and sodium channels in a squid giant axon model.