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1ß Glycine Receptor Function in a Manner Distinct from Propofol





Departments of *Anaesthesiology and
Neurology and Neurophysiology, Hannover Medical School, Hannover, Germany; and
University Department of Anaesthesia, The University of Liverpool, Liverpool, United Kingdom
Gertrud Haeseler, MD, Department of Anaesthesiology, OE 8050, Hannover Medical School, D-30623 Hannover, Germany. Address e-mail to Haeseler.Gertrud{at}MH-Hannover.de
The anesthetic propofol (2,6 diisopropylphenol) mediates some of its effects by activating inhibitory chloride currents in the lower brainstem and spinal cord. The effects comprise direct activation of
-aminobutyric acid-A and glycine receptors in the absence of the natural agonist, as well as potentiation of the effect of submaximal agonist concentrations. Replacement of propofols isopropyl groups by di-tert-butyl groups yields a compound without in vivo anesthetic effects. We have studied the effects of propofol and 2,6 di-tert-butylphenol on chloride inward currents via rat
1ß glycine receptors heterologously expressed in human embryonic kidney cells. Propofol, but not 2,6 di-tert-butylphenol, directly activated glycine receptors; half-maximal current activation was observed with propofol 114 ± 27 µM. Both compounds potentiated the effect of a submaximal glycine concentration (10 µM) to a maximum value of 136% ± 71% (propofol) and 279% ± 109% (2,6 di-tert-butylphenol) of the response to glycine 10 µM. The 50% effective concentration for this effect was 12.5 ± 6.4 µM and 9.4 ± 10.2 µM for propofol and 2,6 di-tert-butylphenol, respectively. Propofol and its nonanesthetic structural analog do not differ in their ability to coactivate the glycine receptor but differ in their ability to directly activate the receptor in the absence of the natural agonist.
IMPLICATIONS: This in vitro study shows that, at the glycine receptor level, propofol does not differ from its nonanesthetic structural analog 2,6 di-tert-butylphenol in its ability to enhance the effect of small glycine concentrations but differs in its potential to directly activate chloride inward currents in the absence of the natural agonist.
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