Differential effects of reproductive and hormonal state on bFGF and GFAP immunoreactivity in the hypothalamus and cingulate cortex of the female rat

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

Pregnancy and Maternal Behavior Induce Changes in Glia, Glutamate and Its Metabolism within the Cingulate Cortex

An upregulation of the astrocytic proteins GFAP and bFGF within area 2 of the cingulate cortex (Cg2) occurs within 3 hours of parturition in rats. These changes are the result of an interaction between hormonal state and maternal experience and are associated with increased dendritic spine density in this area. Here, we examined whether this upregulation of astrocytic proteins generalized to other glial markers and, in particular those associated with glutamate metabolism. We chose glial markers commonly used to reflect different aspects of glial function: vimentin, like GFAP, is a marker of intermediate filaments; glutamine synthetase (GS), and S-100beta, are used as markers for mature astrocytes and GS has also been used as a specific marker for glutamatergic enzymatic activity. In addition, we examined levels of proteins associated with glutamine synthetase, glutamate, glutamine and two excitatory amino acid transporters found in astrocytes, glt-1 and glast. S100beta immunoreactivity did not vary with reproductive state in either Cg2 or MPOA suggesting no change in the number of mature astrocytes across these conditions. Vimentin-ir did not differ across groups in Cg2, but expression of this protein decreased from Day 1 postpartum onwards in the MPOA. By contrast, GS-ir was increased within 24 h postpartum in Cg2 but not MPOA and similarly to GFAP and bFGF this upregulation of GS resulted from an interaction between hormonal state and maternal experience. Within Cg2, upregulation of GS was not accompanied by changes in the astrocytic glutamatergic transporters, glt-1 and glast, however, an increase in both glutamate and glutamine proteins were observed within the Cg2 of postpartum animals. Together, these changes suggest postpartum upregulation of glutamatergic activity and metabolism within Cg2 that is stimulated by pregnancy hormones and maternal experience

Neurobiology of premature brain injury

Every year in the United States, an estimated 500,000 babies are born preterm (before 37 completed weeks of gestation), and this number is rising, along with the recognition of brain injuries due to preterm delivery. A common underlying pathogenesis appears to be perinatal hypoxia induced by immature lung development, which causes injury to vulnerable neurons and glia. Abnormal growth and maturation of susceptible cell types, particularly neurons and oligodendrocytes, in preterm babies with very low birth weight is associated with decreased cerebral and cerebellar volumes and increases in cerebral ventricular size. Here we reconcile these observations with recent studies using models of perinatal hypoxia that show perturbations in the maturation and function of interneurons, oligodendrocytes and astroglia. Together, these findings suggest that the global mechanism by which perinatal hypoxia alters development is through a delay in maturation of affected cell types, including astroglia, oligodendroglia and neurons

Reproductive state changes Glutamine Synthetase-ir within Cg2.

<p>Panel A shows results from the Cg2 and panel B the MPOA. Asterisks denote a significant difference (p<.05) from all other groups. (n = 4 for all groups/area).</p

Levels of glutamate and glutamine protein within the Cg2 change with reproductive state.

<p>Glutamate (A) or glutamine (B) levels were divided by total protein in picograms per microliter. Asterisks denote a significant increase from cycling and mid-pregnant groups. (Cycling, D1, D16 n = 5; Mid-pregnant, Late Pregnant and Hour 3, n = 6)</p

Representative photomicrographs of vimentin-ir in the MPOA.

<p>Panel A shows vimentin-ir of the MPOA of Cycling animals, and Day 16 (MPOA- panel B, Cg2 Panel C). Note the decrease in vimentin-ir within the MPOA during lactation and the relative absence of vimentin-ir cells within Cg2. Panels D and E show darkfield images of S100beta-ir within Cg2 of Cycling (D) and D16 (E) and in the MPOA of an H3 postpartum rat (F).</p

S100beta does not vary with reproductive state.

<p>Panel A shows the mean number of S100beta immunoreactive cells in Cg2 and MPOA (B) in cycling and 3 hours, 4 and 16 day postpartum animals. No significant differences across groups were observed in S100beta levels. However, unlike bFGF and GFAP, S100beta did label astrocytes within the Cg2 of cycling animals. (Cg2: cycling n = 4, H3 n = 4, D4 n = 5, D16 n = 6; MPOA: cycling n = 5, H3 n = 4, D4 n = 4, D16 n = 5)</p

Vimentin-ir cells within the Cg2 and MPOA of cycling and postpartum animals.

<p>No significant changes were observed within Cg2 (A), however, vimentin-ir remained decreased in the MPOA (B) after 24 hours postpartum, suggesting a decrease in immature radial glia in this area during the postpartum period. Asterisks denote a significant difference (p<.05) from all other groups. (Cg2: cycling n = 3, all other groups, n = 4 MPOA: n = 4 for all groups)</p