Increased aversion to bitter-tasting fluids in the Brattleboro rat

Area of Science:

• Physiology
• Animal Behavior
• Endocrinology

Background:

• Brattleboro rats with diabetes insipidus (BDI) exhibit polydipsia, often attributed to vasopressin deficiency.
• Increased fluid consumption in BDI rats may not solely reflect an increased drive to drink.
• Investigating the motivation to drink in BDI rats is crucial for understanding their physiological responses.

Purpose of the Study:

• To assess the drinking motivation of BDI rats compared to Long Evans (LE) rats.
• To determine if BDI rats have a decreased motivation to drink when faced with aversive stimuli.
• To differentiate between physiological thirst and behavioral drive to drink in BDI rats.

Main Methods:

• Administering quinine solutions of varying concentrations as the sole fluid source to BDI and LE rats.
• Measuring 24-hour fluid balance in rats exposed to quinine.
• Conducting two-bottle preference tests with quinine solutions.
• Using sucrose octa-acetate as an alternative aversive taste stimulus.

Main Results:

• BDI rats significantly reduced fluid intake more than LE rats at high quinine concentrations (100 mg/l), indicating reduced drinking motivation.
• BDI rats demonstrated a higher taste threshold for quinine compared to LE rats.
• BDI rats drastically reduced fluid intake when sucrose octa-acetate was the sole fluid source, while LE rats increased consumption.

Conclusions:

• The high water intake in BDI rats is not solely driven by an increased motivation to drink.
• BDI rats exhibit a decreased motivation to drink when presented with aversive taste stimuli.
• Taste aversion plays a significant role in regulating fluid intake in BDI rats, independent of their underlying polydipsia.