The mRNA levels of four EP receptors (EP1–4) were assessed in the different areas of the terminal ileum by means of RT–PCR; the EP2 and EP4 mRNA levels were observed to be increased at the less involved terminal ileum than in the other positions of intestinal tissues and non-NEC controls (Fig. 2E–H). The gene discussed is PTGER4; the disease is necrotizing enterocolitis.