Cocaine-induced behavioral sensitization and conditioning in male Japanese quail.

Repeated intermittent cocaine treatment often results in behavioral sensitization or an augmented response to cocaine. Cocaine-induced behavioral sensitization may be an important contributor to cocaine addiction and abuse. Some studies have also shown that conditioned drug effects may play a role in behavioral sensitization. The current experiment utilized a simplified discrimination paradigm to investigate behavioral sensitization and the role of conditioning in an avian species. Male Japanese quail received alternating injections of cocaine (10 mg/kg i.p.) paired with a context and saline injections paired with a different context. They were later given a cocaine challenge followed by and a saline challenge in the drug-paired context. Results showed that birds that received cocaine paired with one context also demonstrated behavioral sensitization to a cocaine challenge given after a withdrawal period and they developed conditioning to the drug-paired context. A saline control and a control group that received cocaine that was not paired with the test context failed to demonstrate sensitization or conditioning. The findings demonstrate visual discrimination learning and implicate the role of Pavlovian conditioning in behavioral sensitization.

Cocaine sensitization in male quail: temporal, conditioning, and dose-dependent characteristics.

Chronic cocaine administration typically results in increased locomotor activity, known as behavioral sensitization. Investigating the time course of locomotor activity across trials may provide a more detailed analysis of the temporal changes that might occur within sensitization. Prior research with rodents shows that the peak of locomotor activity shifts from acute to chronic drug administration. The purpose of the current experiment was to investigate acute versus chronic cocaine effects on locomotor activity in an avian species, Japanese quail, and to investigate whether this phenomenon is dose-dependent. Subjects received daily i.p. injections of saline or 5, 10, or 20 mg/kg cocaine for 20 days. Following each injection, birds were placed in standard locomotor activity chambers, and activity was recorded for 150 min. A cocaine challenge was given after a ten-day withdrawal period. Two retraining trials were given to re-establish cocaine responding prior to a saline challenge in the drug-paired environment. Results showed that repeated administration of the 10 mg/kg dose of cocaine enhanced activity across 120 min compared with acute administration. In contrast, repeated administration of the 20 mg/kg dose resulted in greater cocaine-induced activity for 60 min compared with acute administration. In addition, behavioral sensitization was shown to be dose-dependent and appeared to be due, at least in part, to conditioning.