Table 1. Summary of the current state of data on pair bonding from prairie voles, titi monkeys, and humans.
Prairie voles | Titi monkeys | Humans | |
Oxytocin | OTRa in the NAcb are crucial to pair bonding based on multiple methods: pharmacology [30], viral vectors [38], RNAic technology [39] | OTR present in some dopaminergic areas, like the LSd [113]; these areas are implicated in imaging studies of pair bonding [105,109]; however, no OTR present in the NAc as in voles | Peripheral OTe responsive to relationship cues [44-46]; intranasal OT enhances partner attractiveness, distance from strangers [52,53]; genotype associations [43]; OTR distribution known only for brainstem [117] |
Vasopressin | AVPR1af in VPg are crucial to pair bonding based on multiple methods: pharmacology [30], viral vectors [41], RNAi technology | Intranasal AVPh causes changes in partner contact [126]; AVPR1a present in NAc rather than VP [113]; these areas implicated in imaging studies of pair bonding [105,109] | Peripheral AVP associated with relationship quality [50,51]; genotype associations [49]; AVPR1a distribution known only for brainstem [117] |
Dopamine | Dopamine type D2 receptors involved in formation [64]; type D1 receptors involved in maintenance via up-regulation of aggression [33] | D1 receptors in LS up-regulated in males after pairing [130]; AVPR1a present in NAc [113] | Dopaminergic areas implicated in imaging studies [62] |
Opioids | µ receptors regulate formation and ĸ receptors regulate maintenance [33,77]; pharmacology, gene expression in striatum | µ and ĸ receptors involved in maintenance, grooming [78] and responses to separation [128] | µ agonism promotes visual attention to faces and eyes [148]; touch from partner alters µ availability [149]; kappa system not studied |
Visual system | Not studied, expected NOT to be heavily involved | Contains OTR and AVPR1a in titis [113] | Not studied directly, involvement expected (but see above) |
aOTR = oxytocin receptor, bNAc = nucleus accumbens, cRNAi = RNA interference, dLS = lateral septum, eOT = oxytocin, fAVPR1a = arginine vasopressin receptor type 1a, gVP = ventral pallidum, hAVP = arginine vasopressin