Effects of Potassium Ions on Action Potential Conduction in A- and C-Fibers of Rat Spinal Nerves

Abstract

Potassium ions in dentifrices for treating 'hypersensitive' dentin are believed to act directly on intradental nerves by raising extracellular potassium 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 compound action potentials (CAP) recorded from rat 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. CAP 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+. CAP attenuation was reversible, and recovery times increased with increasing [K+]o. The effects of KCl and KNO3 solutions were the same for all [K+]o tested. Half-maximal (50%) reduction in the A beta-fiber component of the CAP 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 C-fiber components. Control experiments with glucose and choline chloride 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)

Clinical efficacy of a herbal dentifrice on dentinal hypersensitivity: a randomized controlled clinical trial

“…It has been found that potassium nitrate does not diminish dentine hydraulic conductivity, or promote obstruction of dentinal tubules by the deposition of crystals. 36 According to Wilchgers and Ermert 37 and Kim, 14 potassium nitrate has an effective desensitizing action. The increase in the concentration of extracellular potassium around the nerve fibres causes their depolarization, avoids repolarization and blocks the axonic action and passage of nerve stimulus, thus inactivating the action potential.…”

“…The increase in the concentration of extracellular potassium around the nerve fibres causes their depolarization, avoids repolarization and blocks the axonic action and passage of nerve stimulus, thus inactivating the action potential. 36,37 Moreover, the test group also consisted of 10.0 mg Spinacia oleracea per gram of dentifrice. It has been found that soluble oxalates and oxalic acid in phytocomplexes present in Spinacia oleracea (spinach leaves) form calcium oxalate crystals by reacting with dentinal calcium.…”

Human Dentinal Tubules alterations after desensitizing Dentifrices use: An ex vivo study

“…A substance usually found in this kind of study is a potassium [34,35]. As calcium, the potassium are able to be a reserver of minerals but potassium ions are thought to act by blocking synapses between nerve cells, thereby reducing nerve excitation and the associated pain [34,35].…”

Comparative Evaluation of Efficacy of Two Commercially Available Herbal and Allopathic Dentifrice on Dentinal Hypersensitivity and Their Effect on Plaque and Gingivitis.

“…The increase in the concentration of extracellular potassium around the nerve fibers causes their depolarization, avoids repolarization and blocks the axonic action and passage of nerve stimulus, thus inactivating the action potential. 19,20 .Hence it was shown that group B which contains 5 % of potassium nitrate showed rapid relief in hypersensitivity during 7th day of assessment. In another study which compared HiOra K with that of placebo, Sensitivity scores for controlled air stimulus and cold water were recorded at baseline, 6 weeks and 12 weeks and concluded that test group was found to be significantly better compared to the placebo group at the end of 6 and 12 weeks in reduction of dentinal hypersensitivity.…”

“…It has been found that potassium nitrate does not diminish dentine hydraulic conductivity, or promote obstruction of dentinal tubules by the deposition of crystals. According to Wilchgers 19 and Ermert 20 potassium nitrate has an effective desensitizing action. The increase in the concentration of extracellular potassium around the nerve fibers causes their depolarization, avoids repolarization and blocks the axonic action and passage of nerve stimulus, thus inactivating the action potential.…”