**7.1. AVP and female animal affiliation**

Most of the work on AVP and pairbonding in voles has focused on the male vole. Several studies indicate that OXT is more important than AVP for female pair bonding [169]. It is known that OXT receptor and AVP V1a antagonists prevent pair bond formation in both males and females [170]. Studies of AVP and maternal behavior indirectly support the hypothesis that AVP is a mediator of female affiliation [48, 171], but it is unknown if these effects pertain to adult conspecific affiliation. Additional studies on females are needed to determine if central AVP also is a significant mediator of the female component of pairbonding.

Behavioral Roles of Oxytocin and Vasopressin 61

maternal dam to return to maternal care following a prolonged separation from her pups [68]. Although it has been postulated that maternal nurturing is linked to innate anxiety and OXT and AVP activity, this is based mostly on studies of rodent lines selected for anxiety [175]. Low anxiety mice display lower levels of maternal care compared to high anxiety mice, and acute icv injection of AVP increases maternal care and has anxiogenic effects [176]. These effects in mice were only moderately attenuated by cross fostering. An association between maternal care and innate anxiety was not supported in another study of maternal mice, although V1a receptors were correlated with pup grooming [177]. Animal studies suggest that AVP may be a worthwhile target for the development of treatments for anxiety associated disorders that affect maternal behavior, such as postpartum depression, which is often comorbid with anxiety.

Many of the mechanistic studies of AVP and depression and anxiety have focused on males, and there is a need for more detailed studies in both nulliparous and pregnant and maternal females. As mentioned in the maternal behavior section, high anxiety rats and mice have elevated AVP activity in the PVN and display increased anxiety and depression behaviors [31, 176]. However, recent studies on a novel social stress mediated model for postpartum depression suggest that AVP can increase maternal care in animals subjected to the social stress paradigm that attenuates maternal care and aggression and impairs dam and pup growth during lactation [220]. At the present time, much of the available data on AVP and maternal behavior conflicts with the depression data from males, and treatments with V1a/V1b antagonists aimed at decreasing anxiety may have negative effects on maternal care.

The little work that has focused on AVP and female memory has predominately used pregnant or maternal females. Female V1b knockout mice do not display the Bruce effect, where a previously mated female will block the implantation of fertilized eggs if exposed to an unfamiliar male after mating [178]. This suggests that the female's long-term social memory is impaired. As noted in the maternal behavior section, a V1a antagonist around parturition impairs the ability of a dam to re-initiate maternal care [68]. In general, the available data on AVP and female memory supports the literature from males concluding that AVP mediates various forms of memory consolidation and retention and has particular relevance to social memory. If the role of AVP in memory is substantial in human females, it is possible that depression and anxiety treatments targeted at antagonizing central AVP may

Intranasal AVP has been reported to enhance the encoding of emotional facial expressions in humans [179], as well as improving the recognition of sexual cues [180]. Other studies

**7.4. AVP and female animal models of depression and anxiety** 

**7.5. AVP and female animal learning and memory** 

impair memory processes.

**8. AVP in male humans** 

**8.1. AVP and male human affiliation** 
