Effects of chlordiazepoxide on acquisition and performance of a go-no go successive discrimination task, and on brain biogenic amines in cats

Dose-dependent reversal of chlordiazepoxide-induced discrimination impairment by Ro 15-1788

Chlordiazepoxide (10 mg/kg), administered on eight successive acquisition sessions, impaired a light-cued, successive discrimination in male Sprague-Dawley rats by increasing the number of incorrect responses. The benzodiazepine receptor antagonist Ro 15-1788 (5 and 10 mg/kg) reversed the discrimination impairment and reduced the number of incorrect responses in a generally dose-dependent manner when co-administered with chlordiazepoxide. These findings suggest that the impairment of successive discrimination by chlordiazepoxide is mediated by central benzodiazepine receptor sites. When administered alone, however, the 10 mg/kg dose of Ro 15-1788 (but not the 5 mg/kg dose) produced a mild benzodiazepine-like impairment in discrimination, which was accompanied by a small but significant increase in incorrect responses. These findings suggest that Ro 15-1788 may also have some intrinsic action of its own, which needs to be assessed independently of its use as a mediational research tool.

Effects of benzodiazepines on acquisition and performance: a critical assessment

Evidence related to the effects of benzodiazepines on learning and memory is reviewed in the contexts of human verbal learning studies and animal studies using both aversive and non-aversive paradigms. While the impairment of acquisition by benzodiazepines appears to be a robust phenomenon generalizing across species and experimental conditions, the impairment in the performance of an already-learned task by such drugs appears to be more restrictive and highly dependent upon experimental contingencies. Thus far, performance impairment appears to be found mainly in animal studies using non-aversive, food-motivated tasks, with such tasks being particularly well suited for investigating such a phenomenon. At present, there is a noticeable lack of knowledge regarding the neurochemical substrates underlying BDZ-induced impairment. Finally, some issues that may contribute to the presence or absence of a BDZ-induced performance impairment in published studies are briefly considered.

Dose-dependent impairment in the performance of a go-no go successive discrimination by chlordiazepoxide

After learning a light-cued, go-no go successive discrimination to criterion, male Sprague-Dawley rats received 0, 5, or 10 mg/kg chlordiazepoxide on six performance sessions, followed by two drug-recovery (saline) sessions. Chlordiazepoxide impaired discrimination performance in a dose-dependent manner, with animals in the 5 mg/kg dose condition demonstrating tolerance to the drug after two performance sessions. The degree of discrimination impairment in both drug dose conditions paralleled an increase in responding during no-go phases of the performance task. These findings are consistent with a "disinhibitory hypothesis" of performance impairment and suggest that CDP-drugged animals have difficulty in withholding incorrect responses.

Chlordiazepoxide impairs the performance of a learned discrimination

Chlordiazepoxide (CDP) (5 mg/kg) administered on four of eight sessions significantly impaired the performance of a previously learned, reinforcement-cued discrimination in male Sprague-Dawley rats. On four interspersed vehicle-injection sessions, the performance of subjects demonstrated immediate recovery and was indistinguishable from that of controls (0 mg/kg). An analysis of response components indicated that the impairment in discrimination performance was due to a "disinhibitory" effect of the drug on responding during "no-go" phases of the task. The results are discussed in the context of similarities and differences in the effect of CDP on performance and acquisition.