ABSTRACT
The effects of chronic cocaine administration on the locomotor rhythmic patterns of adult female Sprague-Dawley (SD) rats were recorded using an open-field testing assay. The animals were divided into four groups, control (saline), 3.0 mg/kg, 7.5 mg/kg, and 15.0 mg/kg i.p. cocaine group respectively. On experimental day (ED 1), all animals were treated with saline. On ED 2 to ED 7, either saline or cocaine (3.0, 7.5, or 15.0 mg/kg i.p.) was given followed by three days of no treatment (ED 8 to ED 10). On ED 11, rats were treated as they were on ED 2 to ED 7, i.e. either saline, 3.0, 7.5, or 15.0 mg/kg i.p. cocaine. The locomotor activities of rats were recorded for 23 hours daily, allowing one hour for the animal handling and injections, using open field cages with 16 infrared beams of motion detectors. Any breakages of these beams due to the movement of the animals were recorded and compiled by a computer and analyzed. It was observed that all three doses of repeated cocaine administration (3.0 mg/kg, 7.5 mg/kg, and 15.0 mg/kg i.p. cocaine) significantly alter the locomotor rhythmic activity patterns of the adult female SD rats, which suggest that repeated cocaine exposure modulates body homeostasis.