Alpha 2-Adrenergic Receptors Decrease DNA Replication and Cell Proliferation and Induce Neurite Outgrowth in Transfected Rat Pheochromocytoma Cells


Address for correspondence: Prof. C.S. Flordellis, Department of Pharmacology, School of Medicine, University of Patras-Rion, GR-26504, Greece. Voice: +30-2610-997638; fax: +30-2610-994720.


Abstract: Alpha 2-adrenergic receptors (α2-ARs) have a widespread distribution in the central nervous system (CNS) and affect a number of biochemical and behavioral functions, including stimulation of prefrontal cortex (PFC) and cognitive function. In addition to its role as a classical neurotransmitter, norepinephrine (NE) has been recently shown to exert an important influence on the plasticity in areas of the brain where neurogenesis persists in the adult, notably the subgranular zone (SGZ) within the dentate gyrus of the hippocampus and the olfactory bulb (OB). In regulating adult neurogenesis, the noradrenergic system is functionally integrated with chronic stress and depression. Chronic stress, depression, or depletion of NEin vivosuppress, and antidepressant treatments induce hippocampal neurogenesis by down- or upregulating, respectively, cell proliferation. In the present study we show that α2-AR subtypes promote the differentiation rather than cell proliferation of PC12 cells. It is conceivable that α2-ARs might contribute neurotrophic actionsin vivosynergistically or in permutation with other neurotrophic factors.