Effects of advancing age on cerebrospinal fluid concentrations of prolactin in the female rat

Abstract

Studies were conducted to determine the effects of advancing age on serum and cerebrospinal fluid (CSF) prolactin (PRL) concentrations in the female rat. In young rats with basal serum PRL levels, CSF PRL was maintained at 1.1–2.1% of serum PRL levels. In middle-aged rats, CSF PRL levels and the ratio of CSF to serum PRL was low in rats which maintained estrous cycles, but was increased 4- to 10-fold in rats which were in constant estrus. In aged constant estrous rats, CSF PRL concentrations were increased markedly and the CSF to serum PRL ratio increased to 31%. Collectively, these data indicate that (i) in young female rats, only a fraction of serum PRL reaches the CSF; (ii) that CSF PRL concentrations are low in middle-aged rats which exhibit estrous cycles and (iii) that aging and the constant estrous state are associated with elevated CSF PRL concentrations. As such, the age-related elevation in serum PRL levels and the fraction of PRL which accumulates in the CSF may contribute to the age-related dysfunction in brain PRL-responsive neurons.