The effect of both long-term stay of rats under the specific extreme conditions of light deprivation, and the administration of a melatonin receptor antagonist luzindole on the agerelated pattern of behavioral reactions and psycho-emotional manifestations was studied. The level of the emotional and phobic anxiety state of the animals was assessed in an “Open field” installation in combination with the test “Dark chamber with holes”. We found that in the process of aging, rats kept in standard light conditions (LD) demonstrated a decline in motor activity along with an increase in phobic anxiety reactions. The effect of a prolonged exposure to light deprivation on the psycho-emotional state and motor activity of rats varied depending on the ontogenetic period during which the animals were placed in these specific conditions. At an advanced age, the anxiety level increased in rats kept in the dark since birth (LD/DD) to a greater degree than in the animals exposed to such conditions since prenatal development (DD/DD). The administration of a melatonin receptor antagonist luzindole to animals kept in constant darkness led to an age-related increase in phobic anxiety in the open space (as shown in the “Open Field” test), but had a normalizing effect on the psycho-emotional state of the rats in the “Dark chamber with holes” installation, imitating the animals’ natural shelter. It is concluded that the melatoninergic system, including the pineal gland, melatonin and its receptors, is directly involved in the regulation of the behavior and psycho-emotional state of rats under specific lighting conditions, which are often extreme and harmful for their health.