Ultrasonic vocalization sex differences in 5-HT1A-R deficient mouse pups: Predictive phenotypes associated with later-life anxiety-like behaviors.

Anxiety disorders affect nearly twice as many women as men. However, little is known regarding sex-dependent developmental behavioral differences and whether there is an association with later life anxiety disorders. The present study assessed the developmental-behavioral milestones (DBMs) and their relationship with later life anxiety-like behaviors by comparing postnatal ultrasonic vocalizations (USVs) with open field (OF), elevated plus maze (EPM), and light/dark (LD) anxiety test outcomes using the serotonin 1A receptor knockout (KO) mouse model of anxiety. The USVs and DBMs (i.e., grasping, righting, and startle reflexes) were examined on postnatal day 6 (P6), P8, and P10. Adult anxiety-like behaviors were examined on P60 to compare the genotype and sex-dependent differences in anxiety-like behaviors and to correlate them with the USVs. The total number of USVs observed on P8 correlated with later life anxiety-like behaviors in a genotype-, age-, and sex-dependent manner. Interestingly, female KO (KOF) mice exhibited elevated levels of anxiety-like behavior within the OF, EPM, and LD tests. Additionally, an investigation of the USV subtypes, as well as USV sequence structure and repertoire variation, revealed that the KOF mice produced less complex USVs and complex USV-containing sequences on P10. The present study provides an intriguing, predictive "P8/10-USV-to-P60" anxiety-like behavioral model that may prove useful in future characterization, psychopharmacology, and drug rescue studies directed towards sex-specific anxiety treatment.