A role for serotonin in the mammary gland

In this issue of Developmental Cell, Matsuda et al. describe an unexpected function for the neurotransmitter serotonin in the mammary gland, in which local synthesis of serotonin by the mammary epithelium plays an important role in the negative feedback loop opposing stimulation of mammary gland development and lactation by prolactin. This feedback loop is important for suppression of milk secretion in response to filling of the gland. This novel finding adds to the growing body of evidence for diverse functions of serotonin.