Meeting Abstract
The hormone prolactin (PRL) plays a role in many physiological functions, though perhaps, it is best known for enabling lactation in mammals. PRL also regulates milk production in one of the few species of birds that produces crop milk, the rock dove (Columba livia). Circulating PRL concentrations increase over the course of incubation, peaking around the time chicks hatch and are first provisioned. However, less is known about 1) how reproductive tissues vary in receptor expression of this hormone over the course of reproduction and 2) whether this expression is mediated internally or by external environmental cues. To address this, we quantified gene expression of PRL and its receptor (PRL-R) in the pituitary, a main source of PRL production, and in the crop sac of both sexes during the parental care stage. Because both sexes produce milk and engage in contact-incubation and chick-rearing, we predicted males and females would expresses similar patterns of gene activity, and these patterns would be positively related to circulating PRL concentrations. In addition, we used egg removal and hatchling replacement manipulations during mid-incubation to test whether gene expression is internally or externally driven. In the pituitary, we found that PRL expression was similar in both sexes and mirrored patterns observed in hormone circulation. Upon replacing eggs with hatchlings during mid-incubation, PRL-R expression in the crop sac resembled peak expression observed when chicks hatch. This result suggests changes in crop sac PRL-R gene expression are externally driven, and milk production is influenced by the presence of offspring. Our findings offer a higher resolution and better understanding of the regulatory mechanisms driving rock dove PRL signal and signal sensitivity during lactation.
