Effect of pentobarbital, d-amphetamine, and nicotine on two models of sustained attention in pigeons.

Rationale: The animal literature examining the effects of drugs of abuse on sustained attention has provided conflicting results. One reason for these inconsistencies could be the different type of tasks used to measure sustained attention.

Objective: Acute effects of pentobarbital (0.3, 1, 3, 5.6, 10, and 13 mg/kg), d-amphetamine (0.03, 0.1, 0.3, 1, 3, and 5.6 mg/kg), and nicotine (0.03, 0.1, 0.3, 1, and 3 mg/kg) were compared in two models of sustained attention.

Methods: Dose-response curves were compared in eight male, white Carneaux pigeons trained under a continuous-trial attention procedure and in six male, white Carneaux pigeons trained under a discrete-trial attention procedure. Both procedures required subjects to respond to a variable and brief signal presentation (signal was presented on average every 6.5 s).

Results: Under the continuous-trial procedure, pentobarbital decreased hits as well as increased the number of false alarms and misses at doses that did not impair the ability of the animals to respond. d-Amphetamine and nicotine dose dependently decreased hits and increased misses at doses that did not impair rates of responding. However, neither psychomotor stimulant caused a significant increase in false alarms. Under the discrete-trial procedure, pentobarbital, d-amphetamine, and nicotine decreased hits and correct rejections and increased misses and errors of omission. For the most part, these drug effects occurred at doses that increased the latencies of the animals to respond. When comparing drug effects between the continuous- and discrete-trial procedures, a difference in the false alarm rate was observed.

Conclusions: The present study shows that the continuous-trial procedure was able to detect differences between drug classes that were not apparent under the discrete-trial procedure. Although the lack of a true measure of a false alarm rate continues to be a problem with the continuous-trial procedure, it may be an important procedure for studying the effects of pharmacological agents.