Effects of XXXX ions on action potential conduction in A- and C-fibers of @entity35 spinal nerves.

@entity8119 @entity7183 @entity413 @entity1877 @entity972 @entity35 @entity4338
@entity972 ions in dentifrices for treating 'hypersensitive' dentin are believed to act directly on intradental nerves by raising extracellular @entity972 ion concentration ([K+]o) sufficiently to prevent action potential generation by axonal accommodation. However, the [K+]o necessary to block nerve conduction is not precisely known, nor is it certain that K+ can diffuse from a dentifrice in sufficient amounts to inactivate intradental nerves. To establish more accurately the [K+]o required to block nerve conduction under controlled conditions, we studied the effects of increased [K+]o on the sizes of @entity8119 ( @entity8119 ) recorded from @entity35 spinal nerves in vitro. [K+]o was increased by the addition of either KCl or KNO3 to Krebs' solutions applied to the central portion of the nerves. @entity8119 attenuation increased in a dose-dependent manner as [K+]o was raised in the 8 to 64 mmol/L range, and complete block was generally produced with solutions containing at least 32 mmol/L K+. @entity8119 attenuation was reversible, and recovery times increased with increasing [K+]o. The effects of @entity4338 and KNO3 solutions were the same for all [K+]o tested. Half-maximal (50%) reduction in the A beta-fiber component of the @entity8119 occurred with 17.4 mmol/L K+, and with 17.8 mmol/L and 19.3 mmol/L K+, respectively, for the A delta- and @entity7183 components. Control experiments with @entity413 and @entity1877 confirmed that the conduction block observed with increased [K+]o was not due to increased solution osmolarity or ionic strength.(ABSTRACT TRUNCATED AT 250 WORDS)
