Caesium ions: a glycine-activated channel agonist in rat spinal cord neurones grown in cell culture.
1. The chloride (Cl-) currents activated by caesium ions (Cs+), glycine and gamma-aminobutyric acid (GABA) were compared following their application to rat neurones that had been grown in cell culture. Recordings were made using the whole-cell patch clamp technique under voltage clamp conditions. 2. In spinal cord neurones, bicuculline methiodide antagonized GABA-activated currents more effectively than Cs+ - or glycine-activated currents. However, strychnine was more effective at blocking the currents activated by Cs+ or glycine than those activated by GABA. 3. Of the 3 agonists, only GABA activated currents in cells from the intermediate lobe of the rat pituitary. 4. In spinal neurones the size of the currents activated by 70 mM Cs+ was correlated to the size of the currents activated by 15 microM glycine (P less than 0.005; n = 10, Spearman's rank correlation), but there, was no significant correlation between the size of the currents activated by these agents and 10 microM GABA. 5. The joint application of glycine and Cs+ activated currents that were approximately twice as big as the sums of the currents activated by separate applications of the same doses. This synergism was consistent with Cs+ acting at the same receptor as glycine (7 microM glycine being equivalent to 31 +/- 7 mM Cs+). 6. It was concluded that Cs+ activates the same Cl- channel as the inhibitory neurotransmitter glycine.
Smith
S M
SM
MRC Neuroendocrinology Unit, Newcastle General Hospital, Newcastle-upon-Tyne.
McBurney
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RN
D000818:Animals; D002478:Cells, Cultured; D002586:Cesium / Q000494:pharmacology*; D046508:Culture Techniques; D005998:Glycine / Q000494:pharmacology*; D007473:Ion Channels / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects*; D051381:Rats; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects
D007473:Ion Channels; D002586:Cesium; D005998:Glycine