Mating and Maternal Behavior in Vasopressin 1a Receptor Knockout Syrian Hamsters

Arginine-vasopressin (AVP) and its V1a receptor (V1aR) are important in mediating social behavior through the brain’s social behavior neural network. Knockout of the V1aR via CRISPR-Cas9 in Syrian hamsters (Mesocricetus auratus) has resulted in a range of unexpected behavioral effects, such as increased aggression and social communication behavior (i.e., a scent marking behavior called flank marking). For example, although there is considerable evidence that activation of V1aR is necessary for the expression of flank marking in wild-type (WT) hamsters, paradoxically, V1aR knockout (KO) hamsters exhibit greater flank marking compared to WTs. Given these behavioral effects of V1aR KO and our observations that litters of KO dams were smaller, we wanted to determine the effects of this KO on mating and maternal behavior. To investigate these effects, several mating pairings were made between hamsters of different genotypes: WT female x KO male, KO female x WT male, heterozygote x heterozygote, and a control group of WT females and males that were not bred from heterozygous pairings. To analyze mating behavior, a virgin male was placed in the cage of a virgin female in estrus and mating behavior was recorded for ~30 minutes.  The duration of mounts, ectopic mounts, self-grooming, thrusts, social behavior, nonsocial behavior, anogenital investigation, bicycling, intromissions, and latency to intromission in males was recorded. The duration of lordosis and the latency to lordosis in females was recorded. Upon parturition, female’s maternal behavior, including nursing, pup licking, and time off nest, was observed for 30 minutes every four hours from postpartum day 1-7. When examining mating behavior, we found that wildtype males thrust for 322.72s while heterozygous males thrusted for 226.98s and knockout males thrusted for 200.36s (F(2,7)=4.92,p=0.046). Thrusting behavior is typically associated with sexual satiety, so this suggests that knockout and heterozygous males have different mating behavior and physiology than the wildtypes. Preliminary observations of maternal behavior suggest that the V1aR KO in Syrian hamsters may result in reduced maternal caregiving quality, though data analysis is still ongoing. These findings show that the V1a receptor is important for normal sex and maternal behavior in Syrian hamsters.