Expression of the GFAP Gene During Postnatal Development of the Rat Medulla

In mammals, the brainstem contains several CO2-sensitive respiratory centers that are important for regulating ventilation and thereby, in part, maintaining physiological pH levels. These centers include the nucleus tractus solitarii, the locus coruleus, and the retrotrapezoid nucleus. Although respiratory control centers in the brainstem must function at birth in order for the individual to survive, these regions continue to grow and develop postnatally. Consequently, it is important to understand the ontogeny of the respiratory centers in explaining the genesis of postnatal respiratory responses. The vertebrate central nervous system (CNS) develops through the proliferation of two major cell lines, neurons and glia. One glial cell lineage, astrocytes, has been ascribed many important functions, including regulating the constituents of the extracellular space within the CNS and modulating pH. The ability of astrocytes to regulate extracelluar pH may be important in the response of respiratory control centers in mediating ventilation. Therefore, developmental changes in the glial component of the CNS may be of equal importance to those of the neuronal component. Here, we report on our studies using quantitative immunoblots and in situ hybridization to measure the expression of the glial fibrillary acidic protein (GFAP) gene as a marker for astrocyte differentiation during the postnatal development of the medulla in rat. Increases in GFAP expression occurring by day 11 suggest a proliferation and differentiation of astrocytes during a developmental period when glial cells may begin to regulate extracellular pH and mediate the neuronal processing of chemosensory information.