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PubMed1989

Microelectrode studies of amphotericin B on Na+ and K+ conductance in bullfrog cornea.

Addition of 10(-5) M amphotericin B to the tear solution of an in vitro preparation of the frog cornea increased the transepithelial conductance, gt, and decreased the apical membrane fractional resistance, f(R0), in the presence or absence of tear Na+ and Cl-. In the presence of tear Na+ and Cl-, amphotericin B increased the short-circuit current, Isc, from 3.9 to 8.8 microA.cm-2 and changed the intracellular potential, V0, from -48.5 to -17.9 mV probably due to a higher increase in the Na+ than in the K+ conductance. In the absence of tear Na+ and Cl-, amphotericin B decreased Isc from 5.5 to about 0 microA.cm-2 due to K+ (and possibly Na+) flux from cell to tear and changed V0 from -35.4 to -63.6 mV due to the increase in conductance of both ions. Increase in the tear K+ from 4 to 79 mM (in exchange for choline), in the presence of amphotericin B and absence of tear Na+ and Cl-, decreased f(R0) from 0.09 to 0.06, increased gt from 0.23 to 0.31 mS, increased Isc from 0.63 to 7.3 microA.cm-2, and changed V0 from -65.5 to -17.3 mV due to the change in EK in the presence of a high conductance in the tear membrane. Similar effects were observed with an increase of tear Na+. Results support the concept that the Na+ conductance opened by amphotericin B in the apical membrane is greater than the K+ conductance. Previously observed transepithelial effects of the ionophore may be explained mostly on the basis of its effect on the apical membrane.

Amphotericin B↗
PubMed1983

Selective activation of synapses near the tip of drug-ejecting microelectrode, and effects of antagonists of excitatory amino acids in the hippocampus.

A technique was developed to selectively facilitate transmission through synapses near the tip of a drug-ejecting micropipette by increasing Ca2+ concentration in a small space surrounding the tip. By means of this technique, we found that antagonists of excitatory amino acids, cis-2,3-piperidine dicarboxylic acid, gamma-D-glutamylglycine and glutamic acid diethylester, blocked excitation induced in CA3 neurons by glutamate and by mossy fiber stimulation in thin hippocampal sections of the guinea pig.

Amino Acids↗