Continuous electrophysiological measurements of changes in cell volume of motoneurons in the isolated frog spinal cord.
One type of ion-sensitive micro-electrode (K+ ligand Corning 477317) is sensitive to large quaternary ammonium ions such as choline or tetramethylammonium (TMA+). We have now used such electrodes for continuous electrophysiological measurements of changes in cell volume of motoneurons in the isolated frog spinal cord. The electrodes were double-barrelled with tip diameters of 1 micron. The reference barrel was filled with 100 mM choline or 100 mM TMA+ in 1 M Mg2+-acetate, the sensitive barrel contained the Corning K+ ligand. After the impalement of a motoneuron, choline or TMA+ diffused into the cell and about 1 h later, a steady-state concentration of these ions in the range of 10-20 mM was reached. Following this period, the motoneurons were activated by repetitive electrical stimulation or by application of amino acids via the bathing solution. All these stimuli led to a transient rise of the intracellular concentrations of choline or TMA+ (indicating a cell shrinkage of 3-10% difference to control volume).
Serve
G
G
Physiologisches Institut der Universität München, Federal Republic of Germany.
Endres
W
W
Grafe
P
P
D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D001834:Body Water / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D002794:Choline; D004558:Electric Stimulation; D004594:Electrophysiology / Q000379:methods; D066298:In Vitro Techniques; D009046:Motor Neurons / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D000644:Quaternary Ammonium Compounds; D011893:Rana esculenta; D013116:Spinal Cord / Q000166:cytology*; D013654:Taurine / Q000494:pharmacology
D000596:Amino Acids; D002712:Chlorides; D000644:Quaternary Ammonium Compounds; D013654:Taurine; C027917:tetramethylammonium; D002794:Choline; D011188:Potassium