ISOLATION OF DARP (DOPAMINE-RELEASING PROTEIN) FROM FETAL-RAT BRAIN AND EFFECTS OF DARP IMMUNONEUTRALIZATION ON FETAL MESENCEPHALIC DOPAMINE LEVELS

Recent work from this laboratory suggests a role for a novel dopamine- releasing protein (DARP) during rat fetal development. We have previou sly shown that intrafetal administration of an anti-DARP monoclonal an tibody (DARP mAb) at Embryonic Day 17 (E17) induces fetal resorption i n a dose-dependent manner (Kuhananthan et al., Mol. Cell. Neurosci., 2 , 410-417). In this study we present evidence that (1) DARP is present in the rat brain at E17 and (2) in vivo immunoneutralization of DARP at E17 alters dopamine (DA) levels selectively in the prenatal mesence phalon. Enzyme-linked immunosorbent assay of supernatants of crude fet al (E17) brain homogenates using DARP mAb as a probe detects the prese nce of a DARP-like immunoreactive protein in the E17 rat brain. Purifi cation of these homogenates with concanavalin A and immunoaffinity chr omatography yielded a single 60-kDa protein that displayed dopamine-re leasing activity in an in vitro superfusion assay. In addition, intraf etal administration of DARP mAb at E17 significantly elevated DA level s in the mesencephalon 24 and 48 h postinjection, while decreasing the se levels 72 h postinjection. No changes in DA levels were detected in the diencephalon or in the telencephalon. These findings indicate tha t DARP is present in the rat brain at E17 and may play a role in the d evelopment of dopaminergic neurons of the mesencephalon. (C) 1994 Acad emic Press, Inc.