NT-3: an additional neurotrophin expressed in the adult rat pituitary

Neurotrophins mediate a variety of essential biological functions in the nervous system. Evidence has emerged that this class of proteins is also implicated outside the nervous system, in the pituitary. The study described here aims to understand the expression of neurotrophins in the pituitary. We previously reported the presence of nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF) proteins in association with the thyroid stimulating hormone (TSH) and the corresponding mRNAs in the anterior lobe (AL) of the pituitary of adult rats (1). The present study reveals the expression of NGF and BDNF mRNAs in the intermediate plus posterior lobe (IL+PL) as well, and the previously unidentified NT-3 mRNA in the AL and IL+PL. In addition, NGF, BDNF and NT-3 mRNAs are expressed by dissociated AL cells and IL+PL cells, demonstrating their in situ synthesis in endocrine cells of the gland. These findings are new inference for the investigation of the regulation of the synthesis and the secretion of neurotrophins by pituitary cells, with the goal to gain more insight into their function in the hypophysis.