Socio-affective communication in Tph2-deficient rat pups: communal nesting aggravates growth retardation despite ameliorating maternal affiliation deficits.

Background: A lack of serotonin (also known as 5-hydroxytryptamine, 5-HT) in the brain due to deficiency of the rate-limiting enzyme in 5-HT synthesis, tryptophan hydroxylase 2 (TPH2), was recently reported to result in impaired maternal affiliation across species, including mice, rats, and monkeys. In rodents, this was reflected in a lack of preference for maternal odors and reduced levels of isolation-induced ultrasonic vocalizations (USV), possibly contributing to a severe growth retardation phenotype.

Methods: Here, we tested whether growth retardation, maternal affiliation deficits, and/or impairments in socio-affective communication caused by Tph2 deficiency can be rescued through early social enrichment in rats.