1. Monogamous Behavior in Males prarie vole pine vole california mouse common marmoset montane vole meadow vole white-footed mouse rhesus monkey Monogamous Behavior socially monogamous forms partner preference highly affiliative bi-parental Non-Monogamous Behavior socially promiscuous forms no partner preference asocial non-paternal HORMONAL, GENETIC, and NEURAL mechanisms

2. Affiliative Behavior test Partner Preference test Stranger Exp. Animal PartnerStranger Exp. Animal

3. Partner preference formation in Prarie Voles Stranger Exp. Animal Partner Role for Vasopressin (AVP)? in males: –communication –sexual behavior –aggression –pair bonding HORMONES In voles (and humans) mating stimulates AVP release

4. prarie vole montane vole young et al, nature 1999 Stranger Exp. Animal Affiliative Behavior

5. prarie vole montane vole Lim et al, Nature 2004 V1a receptor expression Ventral Pallidum has higer V1a expression

6. Young and Wang, Nature Neuroscience 2004 V1a receptor gene --V1a receptor protein 99% homologous between vole species --binding kinetics (affinity between hormone and receptor) identical --expression level differences? GENETICS

7. Stranger Exp. Animal Partner partner preference behavior Meadow Vole: role of V1a Inject viral vector into specific brain areas vector contains –lac Z gene (marker) –V1a receptor gene Areas: –ventral pallidum –other areas mate meadow vole –measure partner preference time with partner time with stranger Control injection into VP V1a Injection into other brain areas V1a Injection into ventral pallidum

8. Transgenics in non-monogamous mice Inject prarie vole V1a gene into mouse embryo measure change in affiliative behavior after AVP injection as an adult Stranger Exp. Animal

9. Monogamous Behavior in Males prarie vole pine vole california mouse common marmoset montane vole meadow vole white-footed mouse rhesus monkey Monogamous Behavior socially monogamous forms partner preference bi-parental Non-Monogamous Behavior socially promiscuous forms no partner preference non-paternal HORMONAL, GENETIC, and NEURAL mechanisms HIGHER V1a expressionLOWER V1a expression

10. Ventral Pallidum Part of the reward/reinforcement pathway –in lab rats: cocaine use activates neurons in ventral pallidum infuse psychostimulants directly into ventral pallidum –subjects develop ‘conditioned place preference’ for environment where injections occurred Hypothesis in voles: –V1a in ventral pallidum: activation of this pathway during mating enhances choice of partner later –lack of V1a in non-monogamous voles results in no induction of reward pathway, no preference for partner later NEURAL

11. Summary Vasopressin (AVP) is involved in partner preference and affiliative behavior in monogamous voles Differences in these behaviors between monogamous and non-monogamous species lies in the V1a receptor monogamous voles have a different promoter that increases receptor expression in the ventral pallidum induction of V1a receptor expression in non- monogamous species induces monogamous-like behaior Ventral Pallidum appears to enhance partner preference because it activates the ‘reward pathway’ during mating NEURAL GENETIC HORMONAL

12. V1a viral vector insertion into Prarie vole ventral pallidum increases affiliative behavior without the need for mating first. insertion into caudate putamen doesn’t have this effect # of receptors present associated behavioral response

13. cerebrospinal fluid AVP oxytocin prarie vole with V1a receptor antagonist cerebrospinal fluid (vehicle) V1a receptor antagonist oxytocin receptor antagonist before mating with female after mating with female Winslow et al Nature 1993