Extinction of fear II: Effects of chlordiazepoxide and chlorpromazine on fear and exploratory behaviour in rats

✍ Scribed by R. Kumar

• Publisher: Springer
• Year: 1971
• Tongue: English
• Weight: 901 KB
• Volume: 19
• Category: Article
• ISSN: 0033-3158
• DOI: 10.1007/bf00401946

✦ Synopsis

l~ats avoided a distinctive environment in which they had previously received inescapable electric shocks; the amounts of passive avoidance were taken as indices of the levels of conditioned fear on repeated unpunished tests. Chlordiazepoxide, 7.5 and 15.0 mg/kg tended to reduce fear, but did not accelerate its extinction; 30.0 mg/kg however, retarded the extinction of fear by making the rats inactive and thus reducing the number of unpunished entries into the fear-evoking environment. The effects of chlordiazepoxide on locomotor activity were complex; entries were increased by all three doses of chlordiazepoxide on the first trial only, and following this, activity was markedly depressed by 30.0 mg/kg. Chlorpromazine on the other hand, consistently reduced locomotor activity and at the same time it increased avoidance, possibly by augmenting fear. As a result of this increased avoidance, the extinction of fear tended to be retarded by 1.5 mg/kg of chlorpromazine. The slowing of the "free" extinction of fear by both of these drugs was critically dependent on the doses used, but in no case was there a "beneficial" effect, indicating hastened extinction of fear.