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Cholecystokinin inhibits independent ingestion in neonatal rats
P H Robinson1, T H Moran, P R McHugh
1Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Insights
The gastrointestinal peptide cholecystokinin (CCK) inhibits milk intake in newborn rat pups by acting on the gut. This CCK-8 effect on satiety develops with age and slows gastric emptying.
Area of Science:
- Neuroscience
- Gastroenterology
- Developmental Biology
Background:
- The octapeptide of cholecystokinin (CCK-8) is a gastrointestinal peptide with known satiety functions.
- Its role in early development and the mechanisms underlying its action in neonatal mammals require further elucidation.
Purpose of the Study:
- To investigate the effects of CCK-8 on ingestive behavior and gastric function in neonatal rat pups.
- To determine the age-dependency and specificity of CCK-8's inhibitory actions on feeding.
Main Methods:
- Neonatal rat pups (1-10 days old) were deprived of food for 8 hours.
- Milk ingestion volume and gastric emptying of saline were measured after CCK-8 administration.
- Behavioral observations and administration of desulfated CCK-8 were used to assess specificity.
Main Results:
- CCK-8 significantly reduced milk intake in 1-day-old rat pups, with effective dosage increasing with age.
- CCK-8 suppressed ingestive behaviors specifically and was ineffective when desulfated.
- CCK-8 inhibited deprivation-induced, but not dehydration-induced, milk intake.
- CCK-8 slowed gastric emptying at identical threshold dosages to those inhibiting ingestion.
Conclusions:
- The gastrointestinal peptide CCK is behaviorally and physiologically active in newborn rat pups.
- CCK's satiety action in neonates is supported by its ability to inhibit gastric emptying.
- These findings highlight the role of CCK in regulating feeding behavior and gastric function during early development.
Abstract:
The ability of the octapeptide of cholecystokinin (CCK-8) to inhibit independent ingestion was examined in 8-h deprived 1- to 10-day-old rat pups consuming milk from the surface of a test chamber. CCK significantly reduced the volume of milk ingested in 1-day-old rat pups at a dose of 100 ng/kg. The threshold effective dosage for inhibition of intake increased with age up to 10 days of age. The specificity of this suppression was evaluated in three ways. First, behavioral observation indicated that ingestive but not noningestive behaviors were suppressed by CCK. Second, desulfated CCK-8 was ineffective in suppressing milk ingestion. Finally, CCK inhibited milk intake stimulated by deprivation but did not affect dehydration-induced milk ingestion in 3-day-old rat pups. In addition to inhibiting intake, CCK inhibited the rate of gastric emptying of saline test meals in 1- and 3-day-old rat pups, and the threshold dosages for this suppression were identical to the thresholds for the inhibition of ingestion. These results indicate that the gastrointestinal peptide CCK is both behaviorally and physiologically active in newborn rat pups and support a role for gastric inhibition in the satiety action of CCK.