Age-related decline of vasopressin mRNA in the bed nucleus of the stria terminalis

To determine whether aging influences arginine vasopressin (AVP) biosynthesis in the extrahypothalamic neurons of the bed nucleus of the stria terminalis (BNST), we used in situ hybridization and quantitative autoradiography to compare AVP mRNA in 3-month-old, 14-month-old, and 24-month-old male Fischer 344 rats. As AVP synthesis in the BNST has previously been shown to be steroid-dependent, plasma testosterone (T) was measured by radioimmunoassay. The 24-month-old animals had significantly fewer AVP-labelled cells than either the 3-month-old (p<0.01) or 14-month-old (p<0.05) animals. The cells that were present in the 24-month animals were less intensely labelled than in the other groups, as indicated by a significantly reduced number of grains per cell (p<0.01). Plasma T was also significantly lower in 24-month-old animals when compared with 3-month (p<0.01) or 14-month (p<0.05) groups. The results indicate that there is a marked age-related decline in vasopressin biosynthetic activity in neurons of the BNST.