Depolarization block

Grace AA, Bunney BS, Moore H, Todd CL (1997) Dopamine-cell depolarization block as a model for the therapeutic actions of antipsychotic drugs. TINS 20 31-37... 

In single uterine cells measuring Ca2+ ], simultaneously with ICa and eliciting Ca2+ transients by repetitive membrane depolarizations, blocking the surface membrane Ca-ATPase with carboxyeosin decreased the rate of the decay of the Ca2+ transient by around 30—50%. 

Delayed inactivation of channels in excitable tissnes, cansing repetitive firing and at high doses, depolarization Block GABA-stimnlated chloride uptake Muscle weakness, aching, and tenderness hypotonia... 

C. Atropine will not directly paralyze the respiratory muscles. However, it can prevent the detection of early signs of an overdose of neostigmine, which can quickly progress to a depolarizing block of skeletal muscle and paralysis of the respiratory muscles. Dry mouth, ocular disturbances, and tachycardia are common side effects of atropine given alone, but these effects are less likely to occur with competition between atropine and the increase in the synaptic ACh produced by inhibition of AChE by neostigmine. 

Phenvalera te)] (chlorinated aryl carboxylic acid ester) analogue of Pyrethrin I sensitive TTX-resistant) activator (persistent open state depolarization, block, paralysis) [insecticide, proconvulsant, toxic]... 

It is interesting to note that, even in the absence of lidocaine, the number of responsive channels starts to drop between the resting potential (-70 mV) and the firing level (-55 mV). From this, we would expect a slow, partial depolarization to render the membrane refiactory to excitation. This property of the Nay channels may be important in a phenomenon called depolarizing block in skeletal muscle cells. We will look into this in a later section. 

For control of tachyarrhythmia, calcium channel blockers are used. Blockade of these channels decreases contractility and SA and AV node depolarization. Blocking Pi receptor sites within the myocardium reduces the intracellular calcium concentration and the contractility. The potassium concentration is increased, an undesirable effect when the P2 receptors are blocked. 

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