Effect of insulin and PD 098059 on the response to serotonin in rat choroid plexus cells. (A) Change in intracellular calcium in response to 5-HT in a representative choroid plexus cell. Horizontal bar above the trace indicates bath application of 2 μM 5-HT. (B) Change in intracellular calcium in response to 5-HT after 10 minute treatment with insulin in a representative choroid plexus cell. Horizontal bars above the trace indicate bath application of 10 μM insulin or 2 μM 5-HT. (C) Change in peak intracellular calcium concentration in response to 5-HT with and without insulin treatment and/or PD 098059 pretreatment. Basal intracellular calcium levels averaged 20-50 nM for all groups. The data are presented as mean ± S.E.M. * indicates a statistical difference (P < 0.05) of the insulin treatment group when compared to control.