Effect of HZ166 on the VMR to CRD of neonatal saline- and zymosan-treated rats tested at P60. (A) Neonatal zymosan-treated rats exhibited visceral hypersensitivity characterized by significantly (n=6, p<0.001 vs neonatal saline- treated rats) increased VMR to CRD from 10 mmHg onwards. (B) Administration of HZ166 (10 μg/animal, i.t) to neonatal saline- treated rats produced a significant (n=6, p<0.001 vs pre-HZ166) decrease in their VMR to graded CRD from distension pressure 30 mmHg onwards. (C) However, in neonatal zymosan-treated rats, the same dose of HZ166 did not produce any inhibition of the VMR to CRD. Values expressed as mean ± S.E.M of ‘6’ animals in each group. p≤0.05 was considered significant. * compared with neonatal saline-treated or pre-HZ166 baseline.