Fig. 4: Effects of PACAP38 administration into the PVN on basal and swim stress-induced ACTH levels.

A Schematic illustration of the experimental design with the timeline of blood sampling (red circles), drug infusion (green bar) and stress exposure (orange bar, forced swim, FS). Experiment started with insertion of the infusion device (bilateral injection cannulas connected to a microinfusion pump) at least 1 h before blood sampling started. Drugs were infused automatically at a constant flow rate over a period of 7.5 min without any stressful manipulations (e.g such as capturing or restraining animals) before and during the infusion procedure. Blood samples were collected at regular intervals before drug infusion under basal conditions (−35 and −15 min) and after drug infusion, but before stress exposure (−1 min) and after forced swim stress (10, 30, and 60 min). B Swim stress caused an increase in plasma ACTH levels in both intra-PVN PACAP38 (n = 7) and aCSF-injected controls (n = 7). Compared to controls, intra-PVN PACAP38-injected rats showed higher plasma ACTH levels during and after forced swim stress. However, basal levels did not differ between groups. The green bar indicates timing of intra-PVN infusion, the orange bar the forced swim (FS) stress exposure. Data are expressed as mean ± SEM. *p < 0.05 ****p < 0.0001 compared to basal timepoints (−35 and −15 min) in same treatment group; +++p < 0.001 compared to vehicle-injected controls at same timepoint (two-way ANOVA followed by Bonferroni's multiple comparison post hoc test).