No abstract available.
Cochlear Nucleus ; Patch-Clamp Techniques

Brain ; N-Methylaspartate ; Neurons ; Patch-Clamp Techniques

Action Potentials ; Brain ; Neurons ; Patch-Clamp Techniques

OBJECTIVECurrents contributing repolarization in rabbit ventricular myocyte are very complex since the I(To.s) covers almost the whole repolarization phase of the action potential. The other components of repolarizing currents, as I(Kr) and I(Ks) are small. The purpose of this study is to investigate whether or not there are other currents in rabbit ventricular repolarization.

METHODSIon currents of rabbit ventricular myocyte were recorded using the whole-cell patch-clamp technique.

RESULTSIn the present work, an nonselective cation current was identified by replacing the K(+) with Cs(+) in the bathing and pipette solutions. The outward current elicited by depolarizing potentials could be inhibited by Gd(3+), an effective inhibitor of nonselective cation currents. Depleting Ca(2+) and Mg(2+) in the bathing solution, the amplitudes of this outward current increased by 40%-116% at +60 mV, and adding 2 micromol/L insulin to the solution (with normal concentration of Ca(2+) and Mg(2+) in Tyrode's solution), the amplitude increased by 30%-60% at +60 mV.

CONCLUSIONIt is suggested that a nonselective cation current in rabbit ventricular myocytes may play an important role in the repolarization of the action potential in rabbit ventricle. Changes of nonselective cation current will lead to induce or inhibit arrhythmia.

In this paper we present an easily available method of intracellular dialysis via a microcatheter inserted into glass pipette during patch clamp experiment. An oblique hole through the glass pipette holder (above the lateral hole for cell-seal suction) is drilled, through which a microcatheter (O.D.=0.1 mm) made from the universal pipetter tip by hand-drawing passes and sticks out of the holder mouth in parallel with the Ag-AgCl electrode. With a syringe connected to the microcatheter, substitution of intracellular solution and intracellular dialysis of drugs can be achieved easily. Compared with repatch technique and intracellular solution substitution techniques used abroad, this method operates more easily and can produce more reliable results.
Dialysis ; instrumentation ; methods ; Equipment Design ; Microelectrodes ; Patch-Clamp Techniques ; instrumentation

A USB bus based data interface technology for full auto Patch-Clamp system is discussed in the article. The main controller is CY2131QC (Cypress) and the logic controller is EPM3256A (Altera). Optocouplers are used to get rid of the noise from the interface. It makes the installation of the Patch-Clamp system easier by using the USB bus, and is suitable for the new generation of the Patch-Clamp system with a high speed of 1M bytes/s.
Computer-Aided Design ; Equipment Design ; Patch-Clamp Techniques ; instrumentation ; methods

Patch clamp is a technique that can measure weak current in the level of picoampere (pA). It has been widely used for cellular electrophysiological recording in fundamental medical researches, such as membrane potential and ion channel currents recording, etc. In order to obtain accurate measurement results, both the resistance and capacitance of the pipette are required to be compensated. Capacitance compensations are composed of slow and fast capacitance compensation. The slow compensation is determined by the lipid bilayer of cell membrane, and its magnitude usually ranges from a few picofarads (pF) to a few microfarads (μF), depending on the cell size. The fast capacitance is formed by the distributed capacitance of the glass pipette, wires and solution, mostly ranging in a few picofarads. After the pipette sucks the cells in the solution, the positions of the glass pipette and wire have been determined, and only taking once compensation for slow and fast capacitance will meet the recording requirements. However, when the study needs to deal with the temperature characteristics, it is still necessary to make a recognition on the temperature characteristic of the capacitance. We found that the time constant of fast capacitance discharge changed with increasing temperature of bath solution when we studied the photothermal effect on cell membrane by patch clamp. Based on this phenomenon, we proposed an equivalent circuit to calculate the temperature-dependent parameters. Experimental results showed that the fast capacitance increased in a positive rate of 0.04 pF/℃, while the pipette resistance decreased. The fine data analysis demonstrated that the temperature rises of bath solution determined the kinetics of the fast capacitance mainly by changing the inner solution resistance of the glass pipette. This result will provide a good reference for the fine temperature characteristic study related to cellular electrophysiology based on patch clamp technique.
Cell Membrane ; Electric Capacitance ; Membrane Potentials ; Patch-Clamp Techniques ; Temperature

The inferior colliculus (IC) is a pivot along the central auditory pathway. Using infrared visual whole-cell patch clamp recording technique, we investigated the electrophysiological properties of IC subnuclei neurons. Recordings were made from 88 neurons, including 21 neurons from the dorsal cortex of the IC (ICd), 43 neurons from the central nucleus of the IC (ICc) and 24 neurons from the external cortex of the IC (ICx). Based on the responses to positive current injection, three firing patterns, i.e., onset (6.8%, n = 6), adapting (39.8%, n = 35) and sustained (53.4%, n = 47) patterns, were identified. The hyperpolarization-activated inward current (Ih) could be recorded in half of the neurons (49/88). The sustained pattern occurred in more than half of ICd and ICc neurons (61.9% and 67.4%), while the adapting pattern occurred in majority of ICx neurons (75%). Action potential (AP) threshold and time constant also showed significant differences across neurons from the ICd, the ICc and the ICx. Our results indicate that IC neurons are different in electrophysiological properties across the subnuclei. The variance of the responses may be related to the distinct types of neurons as well as the received projections, which is implicated in the distinct roles of IC neurons in central auditory processing.
Action Potentials ; Animals ; Electrophysiological Phenomena ; In Vitro Techniques ; Inferior Colliculi ; cytology ; Mice ; Neurons ; cytology ; Patch-Clamp Techniques

BACKGROUND: The cardiac electrophysiological characteristics differ significantly among mammalian species or among various disease processes. However, difficulties in the procedures for harvesting and isolating tissue have precluded studies using human cardiac specimens. METHODS: The outward K+ -currents were recorded in human atrial myocytes isolated from patients undergoing open heart surgery. The electrophysiological characteristics of the voltage-dependent outward currents were investigated using a whole-cell patchclamp technique. RESULTS: Using depolarizing step pulses, the transient outward currents were activated within 10 msec, which slowly inactivated thereafter. After inactivation, the sustained components of the outward currents remained for up to 5.0 seconds of depolarizing step pulses. While the inactivating component was almost completely inactivated at potentials >+30 mV, the non-inactivating component showed only 10-15% inactivation. The non-inactivating component was highly sensitive to 4-AP and was inhibited by >80% at a concentration of 0.2 mM, while the inactivating component was inhibited by only 25%. The delayed rectifier potassium currents were not recorded. The ratios of the amplitudes of the inactivating and non-inactivating components varied. CONCLUSION: Two components of the voltage dependent outward K+ currents in human cardiac tissue were identified, which could be separated according to their kinetic and pharmacologic properties.
Atrial Appendage ; Humans* ; Muscle Cells* ; Patch-Clamp Techniques ; Potassium ; Potassium Channels ; Thoracic Surgery

Patch-clamp is used to study all sorts of ionic channels and their regulations with measuring pA current of cell ionic channel, but the fast capacitance (C-fast) compensation and slow capacitance (C-slow) compensation transient currents are caused by measuring objects and measuring instruments themselves which will change the properties of action potentials. The present paper firstly discusses the C-Fast transient currents affecting membrane capacitance and membrane potential, and then draws a conclusion that the changes of membrane potential affect the properties of action potential through analyzing the changes of membrane potential in H-H model. Based on this conclusion, we discuss the influence mechanisms mainly through the analysis of traditional C-fast compensation errors, and focus discussion on the shape of electrode capacitance affecting C-fast. This method can not only improve the compensation speed greatly, but also improve the compensation precision from the electrode shape as much as possible.
Action Potentials ; Electric Capacitance ; Ion Channels ; physiology ; Membrane Potentials ; Neurons ; cytology ; Patch-Clamp Techniques