Differences in corticosterone level due to inter-food interval length: implications for schedule-induced polydipsia

Area of Science:

• Behavioral Neuroscience
• Animal Behavior
• Endocrinology

Background:

• Schedule-induced polydipsia (SIP) is excessive drinking behavior observed under specific feeding schedules.
• The role of stress hormones, like corticosterone (CORT), in SIP is not fully understood.

Purpose of the Study:

• To investigate the impact of different food-reinforcement schedules on plasma CORT levels.
• To explore the involvement of CORT in the development and persistence of SIP.

Main Methods:

• Rats were exposed to fixed-interval (FI) 30s and FI 120s schedules, and a massed-feeding condition.
• Plasma CORT levels were measured on days 3 and 40 of the experiment.
• Experiment 2 assessed CORT levels without water access to isolate drinking behavior.

Main Results:

• The FI 30s schedule, unlike FI 120s or massed feeding, induced SIP from day 3.
• While CORT levels were similar across groups on day 3, only the FI 30s group showed elevated CORT on day 40.
• No significant CORT changes were observed in the FI 120s or massed-feeding groups on day 40.

Conclusions:

• The FI 30s schedule is particularly effective in inducing both SIP and a stress response indicated by elevated CORT.
• Findings suggest that increased CORT levels may play a role in the maintenance of SIP.
• SIP might be linked to anxiolytic-like behavior, with CORT modulation being a potential mechanism.