Fig. 1.

Effect of MPRED treatment and recovery on basal and ACTH induced corticosterone secretion. (A) Schematic representation of the basal ultradian rhythm and ACTH injection experiments using automated blood sampling experiment. (B) Mean ± SEM corticosterone profiles from untreated rats (control group, Ctrl; n = 7), rats treated with methylprednisolone (MPRED) in the drinking water (1 g/L) for 5 days (MPRED treatment group, MP-T; n = 6), and rats treated with MPRED for 5 days and then left to recover for 5 days (MPRED withdraw group, MP-W; n = 7). Individual profiles from rats in each experimental group are reported in Suppl. Fig. 1. Blood samples were collected every 10 min from 07:00 on day 1 for 24 h using an automated blood sampling system. Corticosterone secretion parameters and pulse dynamics characteristics from each individual profile were analysed using the PULSAR algorithm and data are shown in Suppl. Table 2A and B. Gray bar represents the dark period (19:00–05:00). (C) Time course of plasma corticosterone response to ACTH administration (16 ng, i.v.). Data were analysed by repeated measures ANOVA and Tukey post-hoc test. *P < 0.05 vs time 0 (effect of ACTH); ^P < 0.05 vs Ctrl at the same time.