title: Differential effects of short- and long-term zolpidem treatment on recombinant α1β2γ2s subtype of GABA(A) receptors in vitro.
abstract: OBJECTIVE
  Zolpidem is a non-benzodiazepine agonist at benzodiazepine binding site in GABA(A) receptors, which is increasingly prescribed. Recent studies suggest that prolonged zolpidem treatment induces tolerance. The aim of this study was to explore the adaptive changes in GABA(A) receptors following short and long-term exposure to zolpidem in vitro.
  
  
  METHODS
  Human embryonic kidney (HEK) 293 cells stably expressing recombinant α1β2γ2s GABA(A) receptors were exposed to zolpidem (1 and 10 μmol/L) for short-term (2 h daily for 1, 2, or 3 consecutive days) or long-term (continuously for 48 h). Radioligand binding studies were used to determine the parameters of [(3)H]flunitrazepam binding sites.
  
  
  RESULTS
  A single (2 h) or repeated (2 h daily for 2 or 3 d) short-term exposure to zolpidem affected neither the maximum number of [(3)H]flunitrazepam binding sites nor the affinity. In both control and short-term zolpidem treated groups, addition of GABA (1 nmol/L-1 mmol/L) enhanced [(3)H]flunitrazepam binding in a concentration-dependent manner. The maximum enhancement of [(3)H]flunitrazepam binding in short-term zolpidem treated group was not significantly different from that in the control group. In contrast, long-term exposure to zolpidem resulted in significantly increase in the maximum number of [(3)H]flunitrazepam binding sites without changing the affinity. Furthermore, long-term exposure to zolpidem significantly decreased the ability of GABA to stimulate [(3)H]flunitrazepam binding.
  
  
  CONCLUSIONS
  The results suggest that continuous, but not intermittent and short-term, zolpidem-exposure is able to induce adaptive changes in GABA(A) receptors that could be related to the development of tolerance and dependence.
authors.affiliation: Ruđer Bošković Institute, Division of Molecular Medicine, Laboratory of Molecular Neuropharmacology, POB 180, Zagreb, Croatia. Josipa.Vlainic@irb.hr
authors.forename: Josipa
authors.initials: J
authors.lastname: Vlainić
authors.forename: Maja Jazvinšćak
authors.initials: MJ
authors.lastname: Jembrek
authors.forename: Toni
authors.initials: T
authors.lastname: Vlainić
authors.forename: Dubravka Švob
authors.initials: DŠ
authors.lastname: Strac
authors.forename: Danka
authors.initials: D
authors.lastname: Peričić
mesh_terms: D000704:Analysis of Variance; D001667:Binding, Competitive; D018929:Cell Culture Techniques; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D005445:Flunitrazepam / Q000008:administration & dosage / Q000494:pharmacology; D058785:GABA-A Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D057809:HEK293 Cells; D006801:Humans; D011485:Protein Binding; D011725:Pyridines / Q000008:administration & dosage / Q000494:pharmacology*; D011869:Radioligand Assay; D011963:Receptors, GABA-A / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D014162:Transfection; D000077334:Zolpidem
chemical_list: D058785:GABA-A Receptor Agonists; C546240:GABRA1 protein, human; C495710:GABRB2 protein, human; C546279:GABRG2 protein, human; D011725:Pyridines; D011963:Receptors, GABA-A; D005445:Flunitrazepam; D000077334:Zolpidem