scholarly journals The action of alcohols and other non-ionic surface active substances on the sodium current of the squid giant axon.

1983 ◽  
Vol 341 (1) ◽  
pp. 411-427 ◽  
Author(s):  
D A Haydon ◽  
B W Urban
Keyword(s):  
Sodium Current ◽  
Giant Axon ◽  
Squid Giant Axon ◽  
Surface Active ◽  
Active Substances

scholarly journals Analysis of sodium current fluctuations in the cut-open squid giant axon.

1984 ◽  
Vol 83 (2) ◽  
pp. 133-142 ◽  
Author(s):  
I Llano ◽  
F Bezanilla
Keyword(s):  
Sodium Channel ◽  
Sodium Channels ◽  
Sodium Current ◽  
Giant Axon ◽  
Squid Giant Axon ◽  
Statistical Techniques ◽  
Current Fluctuations ◽  
Small Populations ◽  
Squid Axon ◽  
Single Sodium Channel

Patch pipettes were used to record the current arising from small populations of sodium channels in voltage-clamped cut-open squid axons. The current fluctuations associated with the time-variant sodium conductance were analyzed with nonstationary statistical techniques in order to obtain an estimate for the conductance of a single sodium channel. The results presented support the notion that the open sodium channel in the squid axon has only one value of conductance, 3.5 pS.

Beyond Hodgkin and Huxley: Calcium and Calcium-Dependent Potassium Currents

1998 ◽  
Author(s):  
Christof Koch
Keyword(s):  
Sodium Current ◽  
Second Messengers ◽  
Giant Axon ◽  
Firing Frequency ◽  
Squid Giant Axon ◽  
Molecular Techniques ◽  
Calcium Dependent ◽  
Ionic Conductances ◽  
Voltage Dependent ◽  
Set Up

The cornerstone of modern biophysics is the comprehensive analysis by Hodgkin and Huxley (1952a,b,c,d) of the generation and propagation of action potentials in the squid giant axon. The basis of their model is a fast sodium current INa and a delayed potassium current IK (which here we also refer to as IDR)- The last 40 years of research have shown that impulse conduction along axons can be successfully analyzed in terms of one or both of these currents. Nonetheless, their equations do not capture—nor were they intended to capture—a number of important biophysical phenomena, such as adaptation of the firing frequency to long-lasting stimuli or bursting, that is, the generation of two to five spikes within 5-20 msec. Moreover, the transmission of electrical signals within and between neurons involves more than the mere circulation of stereotyped pulses. These impulses must be set up and generated by subthreshold processes. The differences between the firing behavior of most neurons and the squid giant axon reflect the roles of other voltage-dependent ionic conductances than the two described by Hodgkin and Huxley. Over the last two decades, more than several dozen membrane conductances have been characterized (Hagiwara, 1983; Llinás, 1988; Hille, 1992). They differ in principal carrier, voltage, and time dependence, dependence on the presence of intracellular calcium and on their susceptibility to modulation by synaptic inputs and second messengers. Our knowledge of these conductances and the role they play in impulse formation has accelerated rapidly in recent years as a result of various technical innovations such as single-cell isolation, patch clamping, and molecular techniques. We will here describe the most important of these conductances and briefly characterize each one. In order to understand more completely the functional role of these conductances in determining the response of the cell to input, empirical equations that approximate their behavior under physiological conditions must be developed and compared against the physiological preparations. In a remarkable testimony to the power and the generality of the Hodgkin-Huxley approach, the majority of such phenomenological models has used their methodology of describing individual ionic conductances in terms of activating and inactivating particles with first-order kinetics (see Chap. 6).

The mechanisms of sodium current inhibition by benzocaine in the squid giant axon

1987 ◽  
Vol 409 (6) ◽  
pp. 596-600 ◽  
Author(s):  
J. R. Elliott ◽  
D. A. Haydon ◽  
B. M. Hendry
Keyword(s):  
Sodium Current ◽  
Giant Axon ◽  
Squid Giant Axon

Neurofilaments and Paired Helical Filaments

1985 ◽  
Vol 43 ◽  
pp. 740-743
Author(s):  
J. Metuzals
Keyword(s):  
Animal Model ◽  
Posttranslational Modifications ◽  
Posttranslational Modification ◽  
Giant Axon ◽  
Paired Helical Filaments ◽  
Squid Giant Axon ◽  
In Vitro Experiments ◽  
Thin Sections ◽  
Structural Relationships

It has been demonstrated that the neurofibrillary tangles in biopsies of Alzheimer patients, composed of typical paired helical filaments (PHF), consist also of typical neurofilaments (NF) and 15nm wide filaments. Close structural relationships, and even continuity between NF and PHF, have been observed. In this paper, such relationships are investigated from the standpoint that the PHF are formed through posttranslational modifications of NF. To investigate the validity of the posttranslational modification hypothesis of PHF formation, we have identified in thin sections from frontal lobe biopsies of Alzheimer patients all existing conformations of NF and PHF and ordered these conformations in a hypothetical sequence. However, only experiments with animal model preparations will prove or disprove the validity of the interpretations of static structural observations made on patients. For this purpose, the results of in vitro experiments with the squid giant axon preparations are compared with those obtained from human patients. This approach is essential in discovering etiological factors of Alzheimer's disease and its early diagnosis.

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