Angiotensin II increases vesicular trafficking in brain neurons

Our previous studies have established that angiotensin (Ang) LT stimulates the release, uptake, and synthesis of norepinephrine (NE) in brain neurons involving distinct signal transduction pathways. However, little is known i f this NE neuromodulatory effect is a result of Ang II activation of vesicu lar trafficking in the catecholaminergic neurons. Thus, the aim of this stu dy was to determine if Ang II influences movement of vesicles in live neuro ns. Dopamine-beta -hydroxylase (DPH) fused to green fluorescence protein (G FP) has been used to trace vesicular movement in live neurons by confocal m icroscopy. Transfection by a plasmid containing GFP-D betaH resulted in the expression of green fluorescence, representing approximate to 100 kDa GFP- D betaH fusion protein. The fluorescence was predominantly localized in the perinuclear region of the neuronal soma, with a few neurites also depictin g the fluorescence. Ang LT caused a dramatic redistribution of fluorescence . The fluorescence was translocated to the neurites in a time-dependent man ner. As a result, the number of neurites depicting fluorescence was signifi cantly increased. The translocation was blocked by losartan, an Ang n type 1 receptor subtype-specific antagonist and not by PD123319, an Ang II type 2 receptor subtype antagonist. High-magnification confocal microscopic exam ination revealed that Ang II treatment resulted in a distal movement of cer tain fluorescent clusters in the neurites at an average rate of 0.84 +/-0.2 mum/s. These observations suggest increased vesicular trafficking is a key signaling event in Ang II stimulation of NE neuromodulation.