Effects of acute and repeated zolpidem treatment on pentylenetetrazole-induced seizure threshold and on locomotor activity: comparison with diazepam.
Zolpidem and diazepam are widely used drugs acting via benzodiazepine binding sites on GABA(A) receptors. While diazepam is non-selective, zolpidem has a high affinity for alpha1-, and no affinity for alpha5-containing receptors. Several studies suggested that behavioral effects of zolpidem might be more similar to classical benzodiazepines than previously thought. To compare the sedative and anticonvulsant properties of these drugs and to evaluate the importance of GABA(A) receptor subunits for development of tolerance during chronic treatment, we tested the effects of acute and repeated administration of zolpidem and diazepam on ambulatory locomotor activity (a measure of sedation) and on the threshold for myoclonic, clonic and tonic seizures in response to i.v. infusion of pentylenetetrazole (PTZ). Both drugs given acutely in doses 0.3, 1 and 3 mg/kg reduced locomotion, and in doses 1 and 3 mg/kg elevated the threshold for PTZ-induced seizures. The effects of zolpidem and diazepam on the tonic seizure threshold were greater than on myoclonus and clonic seizure threshold. Diazepam and zolpidem (3 mg/kg), given 18 or 42 h after repeated drug treatment (10 days, 5 mg/kg, twice daily), decreased the PTZ seizure threshold and increased the locomotor activity as compared to control mice, indicating development of tolerance to their anticonvulsant and sedative effects. After repeated treatment the PTZ seizure threshold was not different between the two drugs, while differences in sedation became larger than after the acute treatment. The results suggest that alpha5-containing GABA(A) receptors are not crucial for the development of sedative and anticonvulsant tolerance.
Laboratory for Molecular Neuropharmacology, Division of Molecular Medicine, Ruder Bosković Institute, Zagreb, Croatia.
Josipa
J
Vlainić
Danka
D
Pericić
D000818:Animals; D000927:Anticonvulsants / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D003292:Convulsants / Q000008:administration & dosage / Q000633:toxicity*; D003975:Diazepam / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004361:Drug Tolerance; D018755:GABA Agonists / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D058785:GABA-A Receptor Agonists; D006993:Hypnotics and Sedatives / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D008124:Locomotion / Q000187:drug effects; D008297:Male; D051379:Mice; D008808:Mice, Inbred CBA; D009207:Myoclonus / Q000139:chemically induced / Q000517:prevention & control; D010433:Pentylenetetrazole / Q000008:administration & dosage / Q000633:toxicity*; D011725:Pyridines / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D011963:Receptors, GABA-A; D012640:Seizures / Q000139:chemically induced / Q000517:prevention & control*; D000077334:Zolpidem
D000927:Anticonvulsants; D003292:Convulsants; D018755:GABA Agonists; D058785:GABA-A Receptor Agonists; C546241:Gabra1 protein, mouse; C493920:Gabra2 protein, mouse; D006993:Hypnotics and Sedatives; D011725:Pyridines; D011963:Receptors, GABA-A; D000077334:Zolpidem; D003975:Diazepam; D010433:Pentylenetetrazole