A new exposure model to evaluate smoked illicit drugs in rodents: A study of crack cocaine

Abstract

The use of smoked illicit drugs has spread dramatically, but few studies use proper devices to expose animals to inhalational abused drugs despite the availability of numerous smoking devices that mimic tobacco exposure in rodents. Therefore, the present study developed an inexpensive device to easily expose laboratory animals to smoked drugs. We used crack cocaine as the drug of abuse, and the cocaine plasma levels and the behaviors of animals intoxicated with the crack cocaine were evaluated to prove inhaled drug absorption and systemic activity. We developed an acrylic device with two chambers that were interconnected and separated by a hatch. Three doses of crack (100, 250, or 500mg), which contained 63.7% cocaine, were burned in a pipe, and the rats were exposed to the smoke for 5 or 10min (n=5/amount/period). Exposure to the 250-mg dose for 10min achieved cocaine plasma levels that were similar to those of users (170ng/mL). Behavioral evaluations were also performed to validate the methodology. Rats (n=10/group) for these evaluations were exposed to 250mg of crack cocaine or air for 10min, twice daily, for 28 consecutive days. Open-field evaluations were performed at three different periods throughout the experimental design. Exposed animals exhibited transient anorexia, increased motor activity, and shorter stays in central areas of the open field, which suggests reduced anxiety. Therefore, the developed model effectively exposed animals to crack cocaine, and this model may be useful for the investigation of other inhalational abused drugs.