Abstract
Rats were trained to discriminate between saline and either 0.3, 1.0, 3.0 or 6.0 mg/kg of diazepam in a two-choice, discrete-trial avoidance procedure. Diazepam, chlordiazepoxide, flurazepam and pentobarbital occasioned dose-related increases in diazepam-appropriate responding in all four training dose groups. Increasing the training dose of diazepam from 0.3 to 1.0 mg/kg resulted in approximately a 3-fold shift to the right in the dose-effect curves for each of these four drugs. However, increasing the training dose to 3.0 or 6.0 mg/kg did not result in additional, concomitant shifts in these dose-effect curves. Moreover, the dose-effect curves of nine additional benzodiazepine analogs also did not differ markedly in rats trained with either 1.0 or 3.0 mg/kg of diazepam. The nonbenzodiazepines ethanol, phencyclidine, cyproheptadine and ketocyclazocine failed to produce diazepam-like discriminative stimuli in rats trained with either 0.3, 1.0 or 3.0 mg/kg of diazepam. In rats trained with 1.0 mg/kg of diazepam, Ro 11-6896, but not its inactive stereoisomer Ro 11-6893, occasioned diazepam-appropriate responding. Furthermore, the selective benzodiazepine antagonist CGS8216 blocked the effects of diazepam but not the diazepam-like effects of pentobarbital. These results demonstrate that the discriminative effects of diazepam are qualitatively similar across this 20-fold range of training doses; quantitatively, the discriminative effects of diazepam appear to reach a maximum and plateau above a training dose of 1.0 mg/kg in rats.(ABSTRACT TRUNCATED AT 250 WORDS)
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|