SLC18A2 and glioblastoma: Our results revealed that protein expression levels of the four selected markers, namely α1D-adrenergic receptor (ADRA1D), adrenergic ß-receptor kinase 1 (ADRBK1), dopamine receptor D2 (DRD2) and vesicular monoamine transporter 2 (VMAT2), were significantly or tendentiously higher in primary compared to recurrent GBM.