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Postingestive inhibitory controls of independent ingestion in 12-day-old rats
A Weller1, I H Gispan, G P Smith
1Department of Psychology, Bar Ilan University, Ramat Gan, Israel.
Insights
Gastric preloads of saline, glucose, or maltose significantly reduced milk intake in rat pups. Hypertonic solutions indicated additional postingestive inhibitory mechanisms sensitive to osmotic and metabolic properties.
Area of Science:
- Physiology
- Neuroscience
- Behavioral Science
Background:
- Gastric preloads influence subsequent feeding behavior.
- Understanding postingestive feedback mechanisms is crucial for appetite regulation.
Purpose of the Study:
- To investigate the postingestive inhibitory control of ingestion using gastric preloads in young rats.
- To differentiate between preabsorptive and postingestive inhibitory mechanisms.
Main Methods:
- 12-day-old Sprague-Dawley rats received isovolumetric preloads (saline, glucose, or maltose) 5 minutes before an independent ingestion test.
- Milk intake was measured during a 30-minute test period.
- Preloads varied in tonicity and composition (isotonic vs. hypertonic).
Main Results:
- All preloads significantly reduced milk intake compared to controls.
- Isotonic preloads (saline, 5% glucose, 10% maltose) suggest volume-sensitive preabsorptive inhibition.
- Hypertonic preloads (20% glucose, 20% maltose) indicated additional inhibition sensitive to osmotic, saccharidic, or metabolic properties.
Conclusions:
- Both volume-sensitive preabsorptive and postingestive inhibitory mechanisms contribute to satiety.
- The site of action for most inhibition appears preabsorptive, though postabsorptive effects of hypertonic glucose cannot be ruled out.
Abstract:
The postingestive inhibitory control of independent ingestion produced by gastric preloads was investigated in 12-day-old Sprague-Dawley rats. Pups received isovolumetric (5% of body weight) preloads of saline (0.9%), glucose (5%, 10%, or 20%) or maltose (5%, 10%, or 20%) 5 min before a 30-min independent ingestion test in which pups licked milk from the floor of the test chamber. All preloads reduced intake significantly compared to the control condition in which pups were intubated, but no preload was administered. The reduction of intake produced by the isovolumetric, isotonic solutions (saline, 5% glucose, and 10% maltose) is consistent with the stimulation of a preabsorptive, inhibitory mechanism sensitive to volume. The significantly larger reduction of intake produced by isovolumetric, hypertonic solutions (20% glucose and 20% maltose) is consistent with the stimulation of an additional postingestive inhibitory mechanism sensitive to the osmotic, saccharidic, or, in the case of 20% glucose, metabolic properties of these solutions. Because preloads were given 5 min prior to the intake tests, it is likely that the site of action of both inhibitory mechanisms was preabsorptive, although a postabsorptive site for part of the inhibitory effect of 20% glucose cannot be excluded.