Normal food intake and growth in hyperprolactinemic rats

Area of Science:

• Endocrinology
• Neuroscience
• Physiology

Background:

• Normal lactation is characterized by chronic hyperprolactinemia and often increased food intake.
• Previous studies suggested that prolactin (PRL) administration or excess could lead to increased food intake and growth in rats.

Purpose of the Study:

• To investigate the effect of chronic and acute prolactin (PRL) excess on food intake, weight gain, and related physiological parameters in rats.
• To determine if elevated PRL levels, induced by anterior pituitary grafts or direct injections, influence eating behavior.

Main Methods:

• Utilized rats with extra anterior pituitary (AP) grafts under the kidney capsule to achieve chronically elevated circulating PRL levels.
• Administered homologous PRL injections to normal and hypophysectomized rats for 8 days.
• Monitored weight gain, food intake, and fecal weight in grafted and control rats.
• Modified the AP-grafted rat model to assess the impact of PRL-induced hormonal changes (glucocorticoids, estrogens) on eating behavior.

Main Results:

• Rats with chronic hyperprolactinemia (AP grafts) exhibited no significant differences in weight gain, food intake, or fecal weight compared to control muscle-grafted rats.
• Acute PRL injections for 8 days did not lead to increased weight gain in either normal or hypophysectomized rats.
• PRL-induced alterations in adrenal glucocorticoids and estrogens did not provoke changes in eating behavior in the modified AP-grafted rat model.

Conclusions:

• Neither chronic hyperprolactinemia induced by anterior pituitary grafts nor acute hyperprolactinemia induced by rat PRL injections increases food intake or weight gain in rats.
• The findings challenge previous suggestions regarding the role of prolactin in regulating appetite and growth under conditions of excess.