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The effect of the potassium channel blocker, 4-aminopyridine (4-AP), on conduction of action potentials in injured guinea pig spinal cord axons was measured using isolated tracts in oxygenated Krebs' solution at 37 degrees C. The dose-response characteristics of acutely and chronically injured axons were compared. The maximal improvement of conduction(More)
To examine the role of axonal ion deregulation in acute spinal cord injury (SCI), white matter strips from guinea pig spinal cord were incubated in vitro and were subjected to graded focal compression injury. At several postinjury times, spinal segments were removed from incubation and rapidly frozen. X-ray microanalysis was used to measure percent water(More)
We examined the effects of changes in pH(o) and pH(i) on currents contributing to the medium and slow afterhyperpolarizations (mI(AHP) and sI(AHP), respectively) in rat CA1 neurones. Reducing pH(o) from 7.4 to 6.7 inhibited mI(AHP) and sI(AHP) whereas increasing pH(o) to 7.7 augmented mI(AHP) and, to a greater extent, sI(AHP). The ability of changes in(More)
The clearance of extracellular glutamate is mainly mediated by pH- and sodium-dependent transport into astrocytes. During hepatic encephalopathy (HE), however, elevated extracellular glutamate concentrations are observed. The primary candidate responsible for the toxic effects observed during HE is ammonium (NH(4) (+)/NH(3)). Here, we examined the effects(More)
Ammonium (NH(4) (+) ) is required to maintain pathways involved in shuttling metabolic precursors between astrocytes and neurones. Under hyperammonaemic conditions, increases in the cellular influx of NH(4) (+) , and accompanying changes in ion concentrations, may contribute to disruptions in metabolism and neurotransmission. We investigated mechanisms of(More)
1. A threatening visual stimulus frequently elicits the defense response (DR) in crayfish, a behavior that comprises orienting the body to face the stimulus, raising the thorax, and extending and opening the claws. Although this behavior has been reported previously, its kinematics have not been characterized. This work employs kinematic analysis to provide(More)
We examined the potential contribution of a voltage-gated proton conductance (gH+) to acid extrusion from cultured postnatal rat hippocampal neurons. In neurons loaded with Ca2+- and/or pH-sensitive fluorophores, transient exposures to 25-139.5 mM external K+ (K+o) or 20 microM veratridine in the presence of 2 mM Ca2+o (extracellular pH (pHo) constant at(More)
The weak bases NH(3) and trimethylamine (TMeA), applied externally, are widely used to investigate the effects of increasing intracellular pH (pH(i)) on neuronal function. However, potential effects of the compounds independent from increases in pH(i) are not usually considered. In whole-cell patch-clamp recordings from rat CA1 pyramidal neurons, bath(More)
The contributions of HCO(3)(-)-dependent, DIDS-sensitive mechanisms to the maintenance of steady-state pH(i), and the regulation of their activities by cAMP-dependent protein kinase (PKA), were investigated in CA1 neurons with the H(+)-sensitive fluorophore, BCECF. The addition of HCO(3)(-)/CO(2) to neurons with "low" (pH(i) < or = 7.20) and "high" (pH(i) >(More)
The Ca(2+)-dependent slow afterhyperpolarization (AHP) is an important determinant of neuronal excitability. Although it is established that modest changes in extracellular pH (pH(o)) modulate the slow AHP, the relative contributions of changes in the priming Ca(2+) signal and intracellular pH (pH(i)) to this effect remain poorly defined. To gain a better(More)