[The role of visual stimuli in the acquisition of place preference with morphine reinforcement]

In experiments with rats was studied the role of visual stimuli in conditioning of place preference in a T-shaped chamber, certain stimuli being combined with morphine injection (5 mg/kg). Intensity of illumination of the chamber sections, colour of walls, and the orientation of dark stripes on the walls were varied. Testing the animals' behaviour began with determining the reward properties of certain visual stimuli on the basis of the total time of the animals' stay in a chamber. Procedure of combining the visual stimuli with morphine was repeated four times. Associative properties of the stimuli were revealed by comparing the learning efficiency in different experimental groups. Learning within the framework of the place preference model was concluded to depend upon the reward properties of the visual stimuli, whereas the behaviour itself to be based on the mechanism of the instrumental but not the classical conditioned response.