THE EXPRESSION OF SEROTONIN RECEPTORS BY CULTURED RAT SCHWANN-CELLS IS A FUNCTION OF THEIR DIFFERENTIATION - CORRELATION WITH A QUIESCENT MYELINATING PHENOTYPE

Previously we reported that cultured rat Schwann cells express 5-HT2A receptors. In the present study we compared the serotonin-responsivene ss of Schwann cells with their stage of differentiation. Serotonin-res ponsiveness occurred in cells that expressed a myelinating marker but not a nonmyelinating marker. We also examined cells to see if those re sponding to 5-HT were selectively proliferating or quiescent. This was accomplished by pulsing cells with bromodeoxyuridine (BrdUrd), screen ing them for serotonin responses, and then immunolabeling the same cel ls with an antibody recognizing BrdUrd. No BrdUrd+ cells responded to serotonin, whereas most BrdUrd- cells did respond, indicating that ser otonin receptors are expressed in Schwann cells after they become quie scent. Moreover, detection of the responses is enhanced by reducing co ncentrations of mitogen-containing serum in the culture medium. Collec tively, these results suggest that postmitotic Schwann cells express s erotonin receptors while differentiating along the myelinating lineage .