Background: Parkinson’s Disease (PD) is the second most common neurodegenerative disorder in the aging population. Cardinal motor symptoms include slowness of movement, muscle rigidity, tremor and postural instability; caused by death of dopamine cells in the substantia nigra pars compacta (SNpc) of the midbrain. Traditional treatment regimes include administration of levodopa, or dopamine receptor agonists. However these produce side-effects and eventually fail in most patients within 5-10 years [1]. Advances in cell transplantation therapies have shown promising results in alleviation of motor symptoms [2] by providing targeted dopamine delivery. However, several problems need to be overcome for more effective outcomes to be achieved, including; acquisition and maintenance of the dopamine phenotype and integration into the adult midbrain. This is best overcome by learning how new dopamine neurons are normally generated in the adult midbrain. Purpose and Methods: Characterise the electrophysiology of newborn cells in the NesCreERT2/GtROSA++ mouse as they proliferate, migrate and differentiate into dopamine neurons; using whole-cell patch clamping techniques. Results: Recordings were made from regions of the adult midbrain including; lining of the cerebroventricular aqueduct, peri-aqueduct grey (PAG), ventral midline, ventral tegmental area (VTA) and SNpc. Cells displayed a variety of electrophysiological profiles from relatively immature to fully mature neuronal phenotypes. Cells lining the aqueduct exhibited a relatively negative resting membrane potential (n=15,-76.7±1.2mV), small capacitance (6.0±1pF), no action potentials or synaptic activity. In addition they had no apparent voltage-sensitive conductances, typical of an astrocyte like phenotype. YFP+ cells in the PAG (n=8) exhibited a slightly more mature neuronal phenotype with some evidence of voltage-sensitive conductances and larger capacitance values (12.9±4.3pF). They exhibited spontaneous post-synaptic currents (sPSC) in 25% of cells, indicating receipt of synaptic input from other neurons, although only exhibited action potentials in 50% of cells, in contrast to cells in the midline, VTA and SNpc which had actions potentials in all cells. YFP+ cells in the ventral midline through to the SNpc had larger amplitude (midline: 53.4±4.3mV (n=15), VTA: 57.3±3.7mV (n=7), SNpc: 50.2±4.1 (n=9)) and shorter duration (midline: 1.3±0.3ms (n=15), VTA: 1.1±0.2ms (n=7), SNpc: 1.3±0.3ms (n=9)) action potentials, than the aqueduct or PAG region. Finally, YFP+ cells along this gradient also displayed sPSCs in 47% of cells in the ventral midline and 25% of cells in the VTA and 33% in the SNpc. Conclusion: Electrophysiology indicate cells appear to be transitioning from precursors to neurons from the cerebral aqueduct to the SNpc, possibly indicating integration of these new born cells into the dopamine system.