[Reduced waiting capacities as a possible mechanism of action of benzodiazepines. A hypothesis derived from their behavioral effects in animals]

Abstract

In classical punishment procedures, suppression of responding which allows the animal to avoid electric foot-shock is attenuated by benzodiazepines (BZD). Such a release of responding is interpreted as a reflection of the anxiolytic activity of BZD. In these situations however, behavioral suppression also delays the obtention of the food-reward. Therefore, shock-mediated waiting could be as critical a target as shock-induced fear for BZD in punishment procedures. The present study was designed to investigate whether BZD are effective in reducing the capacity of animals to wait for an expected food reward. Fasted rats trained in a T-maze were allowed to choose between two magnitudes of reward: immediate but small (2 pellets) vs delayed but large (8 pellets). Diazepam (2-4 mg/kg), nitrazepam (2 mg/kg), chlordiazepoxide (16 mg/kg) or clobazam (16 mg/kg) decreased the number of times the large reward was chosen by rats subjected to a waiting period of 15 s before having access to the large reward. In conflict situations, rats trained to press a level for food reward were given both 1 pellet and 1 electric foot-shock for pressing during punished periods of fixed duration signalled by a warning stimulus. The diazepam (2 mg/kg)-induced increase in the number of punished presses (anti-punishment effect) was closely related to the percent punishment time within a session. The release of punished responding reached a statistically significant level only when the total punishment-time accounted for at least 40% of the total duration of the session.(ABSTRACT TRUNCATED AT 250 WORDS)