Feedback during exposure to inescapable shocks and subsequent shock-escape performance

Classical conditioning: The new hegemony

Converging data from different disciplines are showing the role of classical conditioning processes in the elaboration of human and animal behavior to be larger than previously supposed. Restricted views of classically conditioned responses as merely secretory, reflexive, or emotional are giving way to a broader conception that includes problem-solving, and other rule-governed behavior thought to be the exclusive province of either operant conditiońing or cognitive psychology. These new views have been accompanied by changes in the way conditioning is conducted and evaluated. Data from a number of seemingly unrelated phenomena such as relapse to drug abuse by postaddicts, the placebo effect, and the immune response appear to involve classical conditioning processes. Classical conditioning, moreover, has been found to occur in simpler and simpler organisms and recently even demonstrated in brain slices and in utero. This target article will integrate the several research areas that have used the classical conditioning process as an explanatory model; it will challenge teleological interpretations of the classically conditioned CR and offer some basic principles for testing conditioning in diverse areas.

O desamparo aprendido revisitado: estudos com animais

O desamparo aprendido tem sido definido como a dificuldade de aprendizagem apresentada por indivíduos que tiveram experiência prévia com estímulos aversivos incontroláveis. O objetivo deste trabalho é fazer uma revisão crítica dos estudos sobre o desamparo aprendido, com animais. Nessa análise, são considerados aspectos conceituais e metodológicos dos estudos em questão e as interpretações teóricas sobre esse efeito comportamental. Aborda-se a evolução histórica desses estudos, bem como alguns aspectos controversos das publicações que se acumularam ao longo de quatro décadas de pesquisa. A associação do desamparo aprendido com a depressão clínica é analisada criticamente, destacando-se a necessidade de maior rigor metodológico e conceitual nos estudos da área.

Stressor controllability, social interaction, and benzodiazepine systems

Effects of benzodiazepine receptor-active compounds on inescapable shock-produced changes in social interaction were studied in the rat. Inescapably shocked animals exhibited less social interaction in a novel situation than did escapably shocked or unshocked rats 24 h after shock. Administration of the selective benzodiazepine receptor antagonist flumazenil at the time of shock prevented the decrease in social interaction. Social interaction was unaffected by the same treatment at the time of measurement. Reduction in social interaction induced by inescapable stress endured for 48-72 h following stressor exposure but was absent 168 h after stress. It was subject to antagonist blockade at all measured time points. Stress-induced decreases in social interaction were also blocked by the benzodiazepine chlordiazepoxide given at the time of shock treatment. The receptor antagonist did not reverse this blockade. An inverse agonist, the beta-carboline FG 7142, administered in place of inescapable shock, produced an identical pattern of social interaction in a dose-dependent manner. The inverse agonist effect was also reversed by the antagonist. The results from antagonist, agonist, and inverse agonist treatments all suggest that an endogenous benzodiazepine receptor inverse agonist is released at the time of inescapable shock and is involved in producing the changes in social interaction subsequently measured.

Impact of psychological dynamics of stress on the peripheral benzodiazepine receptor

In an attempt to dissociate the relative impact of psychological vs. physiological concomitants of stress on the peripheral benzodiazepine receptor (PBR), the influence of stressor controllability and predictability was investigated in rats. In addition, the effect of a purely psychological stressor, contextually conditioned fear, was examined. The response of the PBR in rats confronted with a naturalistic threat, a cat, was also tested. Various peripheral and CNS tissues were analyzed. Specific binding of [3H]Ro 5-4864 was significantly reduced in the kidneys of subjects receiving either controllable or uncontrollable shock. Similar changes were seen in the kidneys of subjects receiving either predictable or unpredictable shock. Mean [3H]Ro 5-4864 binding in lung was reduced following both predictable and unpredictable shock, but only the reduction in the predictable shock group reached significance. Controllability appeared to protect against the stress-induced reduction in [3H]Ro 5-4864 binding in lung. Contextually conditioned fear only affected PBR in the olfactory bulb, and exposure to a cat was without effect. These data suggest that the PBR responds only to potent stressors, and psychological influences on the PBR are tissue specific.

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.