Effects of Librium and shock controllability upon nociception and contextual fear

Controllable shock is known to exert less deleterious effects than does the equivalent exposure to inescapable shock. Recent findings have encouraged speculation that some of these effects may result from differences in the severity of fear produced by the shock experiences. In particular, mediation by gamma-aminobutyric acid has been implicated. In the present experiment, we examined the possibility that chlordiazepoxide (CDP) would attenuate the impact of shock in a manner similar to that of providing control over shock. As shown by others, CDP administered prior to shock treatment blocked the long-term analgesic response, as did the provision of control during shock. Furthermore, whereas animals given controllable shock subsequently exhibited less fear of the shock context than did yoked animals, CDP treatment prior to uncontrollable shock did not appreciably reduce the contextual fear subsequently shown. These results suggest that under some conditions, controllability attenuates the impact of stress by mechanisms other than those shared by benzodiazepine treatment.