Self-administration of morphine in the cat.

Three experiments investigated morphine dependence in the cat. Psychological dependence was measured by self-administration and physiological dependence by induction of withdrawal signs. The data indicate that cats self-administer significantly more morphine than saline. The pattern of morphine self-administrations in cats resembles that which they and other species develop while self-administering psychomotor stimulants. Additionally, although cats develop psychological dependence on morphine and tolerance to some drug effects, little if any physiological dependence, as measured by signs of spontaneous or precipitated withdrawal, is seen. Thus the cat may provide a model system by which the neurobiological phenomena underlying psychological and physiological dependence on morphine may be separated.