title: Effects of repetitive stimulation, veratridine and ouabain on cytoplasmic pH in frog nerve fibres: role of internal Na+.
abstract: Changes of cytoplasmic pH (pHi) in frog nerve fibres during repetitive stimulation have been measured using the fluorescent pH indicator dye fluorescein diacetate (FDA). Under control conditions repetitive (10-50 Hz) stimulation caused only a very small decrease in pHi (by 0.015-0.06 pH units). Modification of Na+ channels by veratridine (VER, 10 microM) greatly increased this stimulus-evoked (SE) internal acidification. Blockade of the Na(+)-K+ pump by ouabain (0.5 mM) enhanced the effects VER and prevented pHi recovery after the termination of repetitive stimulation. A similar inhibition of post-stimulatory recovery of pHi was observed after replacement of external Na+ with Li+, which is not accepted by the Na(+)-K+ pump instead of Na+. These data suggest that SE intracellular acidification in nerves results from or is closely associated with an increase in [Na+]i. Treatments that promote Na+ influx and accumulation of Na+ inside the fibre enhance reduction of pHi. Li+ can be substituted for Na+ in this process.
authors.affiliation: Uljanovsk State Pedagogic Institute, Moscow State University, Russian Federation.
authors.forename: O N
authors.initials: ON
authors.lastname: Valkina
authors.forename: O V
authors.initials: OV
authors.lastname: Vergun
authors.forename: V B
authors.initials: VB
authors.lastname: Turovetsky
authors.forename: B I
authors.initials: BI
authors.lastname: Khodorov
mesh_terms: D000818:Animals; D003593:Cytoplasm / Q000737:chemistry / Q000187:drug effects; D004558:Electric Stimulation; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D009412:Nerve Fibers / Q000187:drug effects* / Q000502:physiology; D010042:Ouabain / Q000494:pharmacology*; D011895:Rana ridibunda; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000187:drug effects; D014701:Veratridine / Q000494:pharmacology*
chemical_list: D010042:Ouabain; D014701:Veratridine; D000254:Sodium-Potassium-Exchanging ATPase