Disappearance of hoarding and disorganization of eating behavior after ventral mesencephalic tegmentum lesions in rats.

The effects of ventral mesencephalic tegmentum (VMT) radio-frequency lessions on spontaneous and complex behaviors, such as food hoarding and alimentary patterns, were investigated. Activity measures indicated that VMT lesions increased horizontal activity in a circular corridor as well as in an open field whereas vertical activity (rearing) was decreased. After 12 hr of food deprivation, food hoarding and alimentary patterns were evaluated in a square open field to which rats had free access from their home cage. Control rats hoarded food and had organized feeding behavior, but experimental rats did not hoard. Moreover, increasing the open-field illumination did not reverse this deficit. Similarly, the VMT lesion induced disruption of the adaptative alimentary behavior in response to food deprivation. A strong correlation was observed between hoarding scores and the extent of locomotor hyperactivity. These results are discussed in terms of a possible implication of limbic-midbrain mechanisms in which the meso-cortico-limbic dopaminergic A10 neurons originating in the VMT might have a primary role.