ROLE OF SEPTAL VASOPRESSIN INNERVATION IN PATERNAL BEHAVIOR IN PRAIRIE VOLES (MICROTUS-OCHROGASTER)

After being paired with females, male prairie voles show major changes in their social behaviors among which is an increase in paternal resp onsiveness. These changes are accompanied by fluctuations in the densi ty of the [Arg8]vasopressin-immunoreactive (AVP-ir) fibers in the late ral septum, suggesting that septal AVP might be involved in these chan ges. To explore a possible involvement of septal AVP in paternal respo nsiveness, we tested whether injections of saline, AVP, or the VI. rec eptor antagonist ta-mercapto-beta,beta-cyclopentamethylenepropionic ac id),2-(O-methyltyrosine]AVP [d(CH2)5Tyr(Me)AVP] into the lateral septu m influenced the four most prominent paternal activities displayed by male prairie voles; grooming, crouching over, contacting, and retrievi ng pups. In a first experiment, sexually inexperienced males received a single injection of AVP, saline, or d(CH2)5Tyr(Me)AVP in the lateral septum, after which their paternal responsiveness was recorded during a 10-min period. AVP-injected animals spent more time contacting and crouching over pups, while d(CH2)5Tyr(Me)AVP-injected animals spent le ss time grooming pups than saline-injected animals. In a follow-up stu dy, one group of animals received an injection of AVP preceded by an i njection of saline or d(CH2)5Tyr(Me)-AVP) Into the lateral septum. A s econd group of animaLs received an injection of saline preceded by an injection of saline or d(CH2)5Tyr(Me)AVP into the lateral septum. In b oth groups, animals spent less time grooming, crouching over, and cont acting pups if they had first been injected with d(CH2)5Tyr(Me)AVP. Co ntrol experiments suggested that the effects of AVP on paternal respon siveness were dose- and site-specific. These data suggest that septal AVP enhances paternal responsiveness by a V1a receptor-mediated mechan ism.