Heterogeneous population of dopaminergic neurons derived from mouse embryonic stem cells: preliminary phenotyping based on receptor expression and function.

The possibility exists that directed differentiation of mouse embryonic stem (mES) cells is capable of yielding enriched populations of dopaminergic neurons, but at present there is little understanding of the pharmacological properties of these cells; or whether such cells represent a pharmacologically, phenotypically similar population. In this study we used a simple culture protocol to generate dopaminergic neurons and offer a preliminary pharmacological investigation of these cells using Ca2+ imaging and [3H]-dopamine release studies. In fluo-4 AM loaded cells, 13-17 days postplating, and after the addition of tetrodotoxin some of the population of mouse embryonic stem cell-derived neurons responded to adenosine triphosphate (ATP), noradrenaline (NA), acetylcholine (ACh) and L-glutamate (L-glut) with elevations of Ca2+ influx. Within the microtubule-associated protein and tyrosine hydroxylase (TH)-positive cell population adenosine triphosphate, noradrenaline, acetylcholine and L-glutamate elicited positive elevations of Ca2+ in 74, 66, 58 and 67% of the population; cells could be further subdivided into three major pharmacologically distinct populations based on the combinations of agonist they responded to. Acetylcholine (30 microM) and noradrenaline (30 microM) were the only agonists to elicit significant tritium overflow from [3H]-dopamine loaded cells. The acetylcholine effect was blocked by atropine (1 microM) and tetrodotoxin (1 microM) and elevated by haloperidol (100 nM). The noradrenaline effects were reduced by cocaine (10 microM), but not by tetrodotoxin (100 nM). These data indicate that the dopaminergic neurons derived from mouse embryonic stem cells represent a heterogeneous population possessing combinations of purinergic, adrenergic, cholinergic and glutamatergic receptors located on the cell soma.