The effects of cocaine on light-induced activity.

Cocaine is a major stimulant drug which can have rewarding and locomotor activating effects. It is used by non-addicts to enhance concentration and performance in a work or social setting. It was suggested that cocaine may amplify the impact of mood and sensory stimulation on behaviour. Here we tested whether cocaine can enhance the impact of novel sensory stimulation on exploratory locomotor activity. In this study the effects of cocaine (0, 2.5, 5.0, 10mg/kg, i.p.) on the locomotor response induced by on-off light stimulation with different light intensities (0, 22, 83, 440 lx) was investigated. Visual stimulation increased locomotor activity and grooming behaviour. Cocaine more dramatically increased locomotion and rearing behaviour but suppressed grooming. Also, visual stimulation effects on grooming were reduced by cocaine. The additive relationship between the cocaine and visual stimulation effects on locomotion and rearing combined with their opposing impact upon grooming point to independent mechanisms mediating cocaine- and visual stimulation-induced behavioural activation.