Abstract

In experiment 1, we compared the effect of hormonal and reproductive state on astrocytic basic fibroblast growth factor (bFGF) and glial fibrillary acidic protein (GFAP) immunoreactivity in various hypothalamic nucleii and the cingulate cortex (CC), area 2. The results of this study showed differential patterns of bFGF and GFAP immunoreactivity across regions examined. Furthermore, a dramatic increase in both bFGF and GFAP within CC in lactating rats on Day 16 postpartum compared to cycling late pregnant and ovariectomized (OVX) rats. In experiment 2a, the dependence of the changes in expression of these proteins in CC on the lactational stage was examined. Six groups of females were included in the study; OVX, cycling and lactating females on Days 4, 10, 16, and 24 postpartum. Brains were processed for bFGF and glial fibrillary acidic protein (GFAP) immunoreactivity. The results of this study showed that all groups of lactating rats showed higher levels of both bFGF and GFAP immunoreactivity than cycling females. Consistent with our earlier study females on Day 16 and 24 postpartum also had higher levels of these proteins than OVX females. Furthermore, Experiment 2b showed that pup removal either on Day 1 or Day 16 postpartum had no effect on GFAP expression in females examined on Day 4 or Day 24, respectively. Together, these data suggest that bFGF and GFAP within the CC is elevated across all stages of lactation. Furthermore, these changes do not correlate simply with hormonal state or the presence of suckling young.