Gamma-aminobutyric acidA receptor function is desensitised in rat cultured cerebellar granule cells following chronic flunitrazepam treatment.
This study examined gamma-aminobutyric acidA (GABA(A)) receptor function in cultured rat cerebellar granule cells by using microphysiometry following chronic flunitrazepam exposure, and correlated the findings with the alpha1 and beta2/3 subunit protein expression and [3H]muscimol binding after the same treatment paradigm. Flunitrazepam treatment reduced (p < 0.05) the maximal GABA-stimulated increase in extracellular acidification rate (Emax) (16.5 +/- 1.2% and 11.3 +/- 1.0%, 2-day control and treated cells, respectively; 17.4 +/- 1.0% and 9.9 +/- 0.7%, 7-day control and treated cells, respectively; best-fit Emax +/- SEM, n = 7), without affecting the GABA concentration required to elicit 50% of maximal response (EC50) (1.2 +/- 1.7 and 2.3 +/- 1.8 microM, 2-day control and treated cells, respectively; 1.7 +/- 1.5 and 1.5 +/- 1.5 microM, 7-day control and treated cells, respectively; best-fit EC50 +/- SEM, n = 7). Flunitrazepam exposure also abolished the flunitrazepam potentiation of the GABA response, caused a transient reduction of the GABA(A) receptor alpha1 and beta2/3 subunit proteins over the initial 2 days, but did not alter [3H]muscimol binding compared with vehicle-treated cells. The results suggest that changes in GABA(A) receptor subunit protein expression, rather than loss of [3H]muscimol binding sites, underlie the chronic flunitrazepam-mediated desensitisation of GABA(A) receptor function.
Brown
M J
MJ
Division of Neuroscience, School of Biological Sciences, University of Manchester, England, UK.
Wood
M D
MD
Coldwell
M C
MC
Bristow
D R
DR
D000143:Acids / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism*; D004357:Drug Synergism; D005445:Flunitrazepam / Q000494:pharmacology*; D018757:GABA Modulators / Q000494:pharmacology*; D009474:Neurons / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000187:drug effects* / Q000502:physiology*; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D000143:Acids; D018757:GABA Modulators; D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid; D005445:Flunitrazepam