MgSO4 has been used for the past two decades as neuroprotective treatment in a variety of preterm conditions. Despite the putative advantages of MgSO4 as a neuroprotective agent in the preterm brain, the short- and long-term molecular function of MgSO4 as a neuroprotective agent has not been fully elucidated. Neuregulin (NRG1)-ErbB4 signaling plays a critical role in embryonic brain development, in the biology of dopaminergic, GABAergic, and glutamatergic systems. We hypothesize that this pathway may be associated with the neuroprotective role of MgSO4. The current study aims to investigate the ability of MgSO4 to modulate the normal developing expression pattern of selected genes related to the NRG1-ErbB, dopaminergic, GABAergic, and glutamatergic systems. We demonstrate that overall short-term treatment of dam rats with MgSO4 affects the expression of fetal brain NRG1, NRG3, ErbB4, GAD67, tyrosine hydroxylase (TH), dopamine D2 and D1 receptors, GluN1, and GluN2B. More specifically, the administration of MgSO4 alters the expression of NRG-ErbB, GAD67, TH, and D2R at early gestation day 16 (GD16) regardless of the activation of the maternal immune system by lipopolysaccharide (LPS). Our data suggest that MgSO4 treatment may affect the expression of major neuronal systems and pathways mostly at an early gestation day. These changes might be an initial clue (foundation stone) in the molecular mechanism that underlies the beneficial effect of MgSO4 as a neuroprotective agent for the developmental brain.