Analysis of the influence of vasopressin neuropeptides on social recognition of rats.

The facilitatory effect of vasopressin neuropeptides on social recognition of adult male rats was analyzed. The decrease of social investigation behaviors during a second encounter with the same juvenile rat served as index for social recognition. Treatment with desglycinamide-(Arg8)-vasopressin (6 mg.kg-1, s.c.) extended the time that adults recognize the same juvenile from 30 min to 24 h. Structure-activity studies revealed that the effect of vasopressin neuropeptides on social recognition resides in the 5-8 part of the AVP molecule. The peptide (pGlu4,Cyt6) AVP-(4-8) was more potent than DGAVP in this behavioral paradigm. These effects bear similarities with the memory enhancing effects of vasopressin neuropeptides as found in other test procedures.