**2.3. OXT and animal paternal behavior**

50 Neuroendocrinology and Behavior

each topic, but will not be comprehensive.

**2.1. OXT and male animal affiliation** 

effects of OXT are conserved across taxa [11].

**2.2. OXT and male animal aggression** 

**2. Oxytocin in male animals** 

of the effects of these peptides on behavior. Although the behavioral roles of OXT and AVP are good examples of effective translation from animal models to clinical study for some topics, such as autism, there is still a need for increased communication and collaboration on many relevant issues, especially gender differences and stress related mood disorders. Both animal and human studies on depression and anxiety indicate that these neuropeptides have gender specific roles, and administering treatments developed in male animals and humans to females may be ineffective or have adverse consequences. The objectives of this review chapter are to present an updated summary of the gender specific behavioral roles of OXT and AVP in both animals and humans and stimulate translationally relevant gender specific studies on these hormones. The need for more female specific studies in this area is great, and this need will be underscored throughout the chapter. Behavioral topics covered include affiliation, aggression, parental behavior, depression/anxiety, and memory. Clinical topics discussed include depression, anxiety, addiction, and autism. Due to the broad scope of these objectives, this review chapter will highlight selected research and review papers on

While most studies of both AVP and OXT conclude that OXT is a more important mediator of affiliative behavior in females than males, there is considerable evidence that OXT may serve important social behavior functions in males as well. The most convincing evidence for the role of OXT in affiliative behavior in animals is pair bonding in prairie voles (*Microtus ochrogaster*). These voles are relatively unique in their monogamous social structure, which is mediated by OXT and AVP activity in the brain. Central OXT infusions facilitate prairie vole pair bonding [3], which has been linked to gender specific developmental effects in male voles [4]. The distribution of OXT receptors in the brain mediates divergent social strategies in monogamous and polygamous vole species [5]. Studies of social recognition and memory in male mice, processes important for the establishment of affiliative behavior, conclude that OXT actions on social behavior are mediated by changes in recognition and social memory [6, 7]. In male rats, OXT facilitates sexual behavior through actions in the PVN [8]. In pair bonded tamarin monkeys, peripheral OXT levels vary with levels of affiliation and sexual behavior in both genders [9]. Specifically, OXT levels in male tamarins were correlated strongly with sexual behavior. In fish it has been postulated that isotocin (the teleostean homologue of OXT) is involved in courtship displays and territorial defense [10], and many of the social behavior

The recent data from stickleback fish suggest that the affiliative actions of OXT in vertebrates are associated with aggression [10]. OXT levels are highest in male sticklebacks that aggressively defend eggs and in subordinate males that fight to change their social status. Disruption of the OXT gene in male mice decreases aggression [12], yet OXT In polygamous male meadow voles (*Microtus pennsylvanicus*), paternal experience is associated with increases in OXT receptor binding in the accessory olfactory nucleus, bed nucleus of the stria terminalis, lateral septum, and lateral amygdala [14]. It was concluded that central OXT infusion increased the tolerance of the offspring by the father. Combined treatment with both an OXT antagonist and an AVP antagonist decrease male parental behavior in reproductively naïve male prairie voles, where treatments with only one antagonist did not affect the expression of alloparenting [15]. It appears that male prairie vole paternal behavior may rely on the neural effects of both peptides. Mandarin voles (*Lasiopodomys mandarinus)*, which are biparental and express parental behavior towards foster pups, increase central OXT expression following the development of male alloparental behavior. This increased expression may be mediated by elevated estrogen receptor alpha [16]. In support of this association between OXT and mammalian paternal expression, a recent primate study reported that icv OXT increased the transfer of food from fathers to their offspring [17]. Similar effects of OXT in male primates are supported by clinical data which will be discussed later in this review.
