Septal vasopressin modulates social memory in male rats.

Adult male rats that are confronted with a sexually immature conspecific display a dramatic reduction in investigatory behavior upon re-exposure to the same juvenile when this exposure takes place 30 min after the initial exposure, but not when it is delayed by an interval of 2 h. This behavioral change may be used to measure the duration of the memory that the test animal forms of the stimulus animal. Vasopressin injected directly into the lateral septum of adult male rats at a dose of 0.1 ng facilitated this form of memory, whereas local injection of a specific hydrophilic vasopressor antagonist, desGlyNH2d(CH2)5Tyr(Me)AVP, impaired it. These findings suggest that vasopressinergic innervation of the lateral septum may be physiologically involved in the modulation of social memory in male rats.