To study the role that the novel nongenomic membranous estrogen receptor GPR30 plays in the hippocampal synaptic plasticity, the developmental profile and subcellular localization of GPR30 in the hippocampus of postnatal female rats was examined by nickel-intensified immunohistochemistry and immunoelectronic microscopy. Results showed that the immunoreactivity of the GPR30 was predominantly localized in the neurons of the hippocampal pyramidal layer of the CAs and grannual layer of the dentate gyrus, and an increased profile with postnatal development was also noticed. GPR30 immunoreactivity was first detected at P7 in the CA2, at P14 it was detected in the CA1, CA2 and dentate gyrus, hereafter it was detected in the CA1, CA2, CA3 and dentate gyrus with higher expression in the adults (P60). Under light microscopy GPR30 immunopositive materials were found in the cytoplasm of the neurons, while under electronic microscopy they were localized in the membranous structure of the neuronal cytoplasm, predominantly the rough endoplasmic reticulum. The above results demonstrated that GPR30 is a membranous estrogen receptor, showing an increased expression profile in the hippocampus of postnatal female rats, it may mediate the rapid, non-genomic effect of estrogen on the morphology and function of the hippocampus, such as morphological maturation, synaptic plasticity, learning and memory.