Septal vasopressin induced preservation of social recognition in rats was abolished by pinealectomy.

The role of intraseptal vasopressin (AVP) and the pineal gland in the modulation of social memory was investigated. For social recognition, male pinealectomised (Px) and sham-operated (SO) rats were confronted with juveniles for 4 min, and injected with either 200 pg AVP or 5 ng of its V1 receptor antagonist d(CH2)5Tyr(Me)AVP (AAVP) into the mediolateral septum. Re-exposure to the same and a different juvenile took place after 30 or 120 min. In SO rats, the social memory was facilitated after injection of AVP (120 min) and impaired after AAVP application (30 min). In Px rats, however, neither AVP nor AAVP administration influenced the social memory. Comparison between SO and Px control groups treated with artificial cerebrospinal fluid did not reveal any differences as to social recognition responses. After subcutaneous administration of 250 microg melatonin (substitution for pinealectomy) the social discrimination responses in Px rats after peptide application were influenced in a manner identical to that noted in SO animals. These findings suggest that the modulation of social memory by intraseptal AVP is dependent on an intact pineal function.