receptor expression in PC-3 cells: effect of EGF. Cells were incubated for 3 weeks in the absence or presence of EGF (10 ng/ml). The x-axis shows the CB1 receptor expression, normalised to β-actin for the individual samples, colour coded on the basis of their experimental series. The y-axis shows the CB1 receptor expression, normalised to β-actin, in the presence of EGF as a ratio of the expression from another well in the same culture plate cultured in the absence of EGF. The dotted line is at a value of unity, i.e. no stimulation of CB1 receptor expression by EGF. The Spearman rho values are shown in the Panel.