Figure 4.

PKC-mediated rundown of recombinant KAR responses to KA in the neuroblastoma cell line SHSY5-Y. (A) Under the conventional whole-cell configuration, cells transfected with different combinations of KAR subunits were exposed to the phorbol ester PdBu (1 μM) for 3 min, and the degree of current attenuation was determined. (B) The maximum level of rundown was seen with homomeric GluR5-2b receptors, on which the inactive analogue of phorbol ester, 4α-PdBu, had no action. Bars represent the degree of rundown observed for the receptors as the mean±s.e.m. of 4–12 experiments. The inset shows that under perforated whole-cell configuration, repetitive activation of GluR5 induced a G-protein-dependent rundown of kainate-induced responses, indicating the reproduction in a heterologous system of the main properties of KAR signalling observed in neurons.