Single potential-dependent K+ channels and their oligomers in molluscan glial cells.

Single K+ channels were studied using the patch-clamp method. A potential-dependent K+ channel of large conductance (about 100 pS at 100 mM of KCl on both membrane sides) was detected. Some properties of the channel (current-voltage relations, kinetic parameters, etc.) are presented. The channel was found to have about 16 resolvable quantized conductance substates. The data are confirmed by spontaneous channel degradation, i.e., spontaneous splitting of the channel conductance into independent conductance oligomers. Some properties of the conductance oligomers of different order are described. The degree of potential dependency of the conductance oligomer parameters is a function of potential dependency. The data obtained are in agreement with a hypothesis that the channels studied are clusters (aggregates) of elementary channel subunits.

The potential-dependent K+ channel in molluscan neurones is organized in a cluster of elementary channels.

Single potential-dependent K+ channels were studied using the patch-voltage-clamp method. Two types of channel with identical, but oppositely directed, potential dependences were found. The channels of the first type (slow channels) are assumed to be responsible for the outward rectification. The properties of the channels of the second type (fast channels) are similar to those of the K+ channels in neurone soma which create the fast transient currents. The kinetic characteristics of both types of channel are presented. The conductances of slow and fast K+ channels are approx. 30 and 40 pS, respectively, at zero membrane potential and a K+ concentration of 50 mmol/l at the inner side of the membrane. The following sequence of channel selectivity with respect to monovalent cations was found: T1+ greater than K+ greater than Rb+ much greater than Cs+ approximately equal to Li+ approximately equal to Na+. The probability of the channel open state monotonically decreases with free Ca2+ concentration at the inside membrane surface for both types of channel. It was found that the channels have discrete and multiple conductance substates . It is supposed that a unitary K+ channel consists of approx. 16 elementary ones with conductances of approx. 2 pS (slow channels) and approx. 2.5 pS (fast channels) at zero potential. At +100 mV the elementary conductances are equal to approx. 4 and 5.5. pS, respectively. Thus, according to this assumption, the unitary channel is a cluster of elementary channels.

Trypsin-induced masking of tetrodotoxin receptor of the sodium channels in mollusc neurons.

At the early stage of trypsin treatment of mollusc neurons tetrodotoxin cannot block the Na+ current. In the course of further exposure of neurones to trypsin, tetrodotoxin-sensitivity is restored completely, so its temporal loss results from shielding rather than destruction of the tetrodotoxin-binding site. Pronase and papain do not affect the tetrodotoxin action on the Na+ current.

Dual effects of microwaves on single Ca(2+)-activated K+ channels in cultured kidney cells Vero.

Using the patch voltage-clamp method, possible effects of millimetre microwaves (42.25 GHz) on single Ca(2+)-activated K+ channels in cultured kidney cells (Vero) were investigated. It was found that exposure to the field of non-thermal power (about 100 microW/cm2) for 20-30 min greatly modifies both the Hill coefficient and an apparent affinity of the channels for Ca2+(i). The data suggest that the field alters both cooperativity and binding characteristics of the channel activation by internal Ca2+. The effects depend on initial sensitivity of the channels to Ca2+ and the Ca2+ concentration applied.

Preliminary microwave irradiation of water solutions changes their channel-modifying activity.

Earlier we have shown that millimetre microwaves (42.25 GHz) of non-thermal power, upon direct admittance into an experiment bath, greatly influence activation characteristics of single Ca(2+)-dependent K+ channels (in particular, the channel open state probability, Po). Here we present new data showing that similar changes in Po arise due to the substitution of a control bath solution for a preliminary microwave irradiated one of the same composition (100 mmol/l KCl with Ca2+ added), with irradiation time being 20-30 min. Therefore, due to the exposure to the field the solution acquires some new properties that are important for the channel activity. The irradiation terminated, the solution retains a new state for at least 10-20 min (solution memory). The data suggest that the effects of the field on the channels are mediated, at least partially, by changes in the solution properties.

Single Cl- channels in molluscan neurones: multiplicity of the conductance states.

Properties of the single Cl channels were studied in excised patches of surface membrane from molluscan neurones using single-channel recording technique. These channels are controlled by Ca2+ and K+ acting on cytoplasmic and outer membrane surfaces, respectively, and by the membrane potential. The channels display about 16 intermediate conductance sublevels, each of them being multiples of approximately 12.5 pS. The upper level of the channel conductance is about 200 pS. The channel behavior is consistent with an aggregation of channel-forming subunits into a cluster.