Autoradiographic study of [ [formula omitted]]flunitrazepam binding sites in the subnuclei of the thalamus of rats rendered tolerant to and dependent on pentobarbital

• Published in: European journal of pharmacology 1998-08, Vol.354 (2), p.145-151
• Main Authors: Suzuki, Toshihito, Ito, Takehiko, Wellman, Susan E., Ho, Ing K.
• Format: Article
• Language: English
• Subjects: Animals; Autoradiography; Benzodiazepine; Binding Sites; Biological and medical sciences; Dependence; Drug Tolerance; Drug toxicity and drugs side effects treatment; Flunitrazepam - pharmacokinetics; GABA Modulators - pharmacokinetics; Hypnotics and Sedatives - pharmacology; Male; Medical sciences; Miscellaneous (drug allergy, mutagens, teratogens...); Pentobarbital; Pentobarbital - pharmacology; Pharmacology. Drug treatments; Radionuclide Imaging; Rats; Rats, Sprague-Dawley; Receptors, GABA-A - metabolism; Substance-Related Disorders - metabolism; Thalamic Nuclei - diagnostic imaging; Thalamic Nuclei - metabolism; Thalamus; Tissue Distribution; Tolerance; Tritium
• ISSN: 0014-2999; 1879-0712
• DOI: 10.1016/S0014-2999(98)00447-6

We examined changes in benzodiazepine binding sites labeled by [ 3 H ]flunitrazepam in five nuclei of the thalamus, the central medial, central lateral, intermediodorsal, ventroposterior, and laterodorsal nuclei, in rats made tolerant to and dependent on pentobarbital. Animals were made tolerant by intracerebroventricular infusion with pentobarbital (300 μg (10 μl) −1 h −1 for six days) through pre-implanted cannulae. Pentobarbital dependence was assessed 24 h after abrupt withdrawal from pentobarbital. Pentobarbital-tolerant rats showed no significant change in [ 3 H ]flunitrazepam binding sites ( B max and K d) in any nucleus examined in the thalamus. In the rats made dependent on pentobarbital, significant increases in the B max of [ 3 H ]flunitrazepam binding without changes in K d were noted in central medial and central lateral nuclei. GABAergic (γ-aminobutyric acid) neurons in the ventrobasal nucleus and in nuclei in the midline group are important in seizure regulation and arousal. These findings suggest that alterations of benzodiazepine receptors in certain nuclei of thalami are involved in the physiological changes induced by pentobarbital dependence. There were no changes in the binding parameters for [ 3 H ]flunitrazepam in pentobarbital-tolerant rats.