Tuberoinfundibular Peptide of 39 Residues (TIP39): A New Player in the Translation of Sensory Input to Prolactin Release during Lactation

Abstract

Lactation is an important reproductive state for all mammalian species. Nourishment of the young is provided by maternal milk and thus competent lactation is necessary for the survival of most mammalian species. Although not now required for survival of human infants, breast milk is considered the most nutritionally complete foodfornewborns.Prolactinplaysessentialrolesinmammary gland development and the production of nutritional components of maternal milk, most notably milk proteins. The stimulus for prolactin release is the suckling of the young on sensory mechanoreceptors in the mammaryglandtogenerateaneuralsignal,whichistranslated into a hormonal signal with the suckling-induced release of prolactin and oxytocin. The neural signal is sent through sensory tracts in the spinal cord, brainstem, and thalamus and eventually elicits the release of prolactin from the pituitary gland through the involvement of hypothalamic neuronal groups (1–5). The control of prolactin secretion during this reproductive process is complex and at times seems to have redundancyingrainedinthesystem(6–8).Thus,allofthe playersinthisimportantreproductiveprocesshavenotyet been identified and placed in their proper sequence. The