Effects of aging on the expression of neurotrophins and their receptors in the rat pituitary gland.

We studied the effect of aging on the mRNA levels of neurotrophins and their receptors in the rat pituitary gland using in situ hybridization. In 2-month-old rats, mRNA for brain derived neurotrophic factor (BDNF) was observed in the anterior and intermediate lobes of the pituitary. TrkB and trkC, the putative receptors for BDNF and neurotrophin-3, were also expressed in the pituitary. In contrast, trk mRNA could not be detected in any of the pituitaries studied. Aging did not affect BDNF mRNA levels. In 2-year-old rats, trkB and trkC mRNA levels were decreased in the anterior lobe. TrkB mRNA levels decreased also in the neural lobe. These results show that although the expression of BDNF does not change during aging in the pituitary, expression of trkB and trkC mRNAs are altered in senescence. These changes may reflect overall impairments in pituitary endocrine functions in old age or they may be associated with morphological alterations in pituitary innervation.