Circulating oestrogen is believed to modulate autonomic function via the α and β subtypes of conventional nuclear oestrogen receptor (ER) but relatively few central autonomic neurones have been shown to express either of these ER subtypes (Gerrits et al. 2007). Recent evidence demonstrates that an orphan G protein-coupled receptor GPR30 (also known as GPR41) can function as a membrane oestrogen receptor (Revankar et al. 2005) and that GPR30 immunoreactivity (-ir) is expressed in the brain (Brailoiu et al. 2007), so raising the possibility that GPR30 could mediate central autonomic effects of oestrogen. This study was designed to examine the expression and localisation of GPR30 in ‘autonomic’ areas of the brain stem and hypothalamus in male and female rats, using two methodological approaches: (1) fluorescence immunohistochemical localisation of GPR30 protein using a rabbit antibody on sections of perfused fixed brain (anaesthesia 5% halothane in 95% oxygen), and (2) RT-PCR and quantitative real-time PCR (qPCR) to assess GPR30 mRNA expression in tissue punches of brain areas of rats (killed by decapitation), including females at different stages of the oestrus cycle. GPR30-ir was typically punctate and cytoplasmic within neurones in a number of brain areas associated with autonomic pathways: nucleus of the solitary tract (NTS), dorsal vagal nucleus, nucleus ambiguus, ventrolateral medulla (VLM) and paraventricular, periventricular and lateral hypothalamic nuclei. The circumventricular organs, including the area postrema, subfornical organ and subcommissural organ displayed intensely GPR30-ir cells. Dual confocal labelling revealed that GPR30-ir was present in a number of identified cell phenotypes, including cholinergic, catecholaminergic and nitrergic neurones, and that GPR30-ir neurones were mostly distinct from those expressing ERα or ERβ. RT-PCR detected GPR30 expression in all of the brain areas examined in both male and female animals. The qPCR results indicated that GPR30 mRNA expression was similar in all brain areas examined in males and metoestrus females; however, marked increases in GPR30 expression were found over the 4 stages of the oestrus cycle. Significantly higher GPR30 mRNA levels (p < 0.05; ANOVA, n=5) were observed in the medulla oblongata, NTS, VLM and hypothalamus of oestrus females when compared to metoestrus. These observations are consistent with the view that GPR30 expressed on neuronal membranes in a number of brain areas may have a role as a rapid transducer responding to plasma oestrogen levels and may thereby modulate the activity of central nervous pathways that regulate autonomic function.