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Ontogeny of hypertonic preabsorptive inhibitory control of intake in neonatal rats
A Weller1, L Tsitolovskya, I H Gispan
1Developmental Psychobiology Laboratory, Department of Psychology, Bar Ilan University, Ramat Gan 52900, Israel.
Insights
Young rats develop inhibitory control over eating as they mature. By postnatal day 12, osmotic load and volume significantly reduce intake, a control not fully present at postnatal day 6.
Area of Science:
- Neuroscience
- Developmental Biology
- Physiology
Background:
- Postingestive feedback mechanisms regulate food intake.
- Ontogenetic development of inhibitory control is crucial for survival.
- Osmotic and volumetric cues are key postingestive signals.
Purpose of the Study:
- To investigate the developmental trajectory of postingestive inhibitory control in rats.
- To determine the emergence of osmotic and volumetric controls of ingestion.
- To examine the influence of deprivation duration on these controls.
Main Methods:
- Rats were tested on postnatal days 6 (P6) and 12 (P12) after varying deprivation periods (6 or 24 hours).
- Gastric preloads of water, varying concentrations of mannitol (osmotic load), or sham preloads were administered.
- Ingestive behavior was measured during a subsequent 30-minute intake test.
Main Results:
- Volumetric control (0.25 M mannitol) emerged by P12, significantly reducing intake, but was absent at P6.
- Hypertonic mannitol (0.5-1.0 M) suppressed intake at P12 under both deprivation conditions.
- At P6, hypertonic control was only observed after prolonged (24h) deprivation, indicating a delayed development.
Conclusions:
- Postingestive inhibitory control, both volumetric and osmotic, undergoes significant ontogenetic development between P6 and P12 in rats.
- Osmotic control is initially dependent on prolonged deprivation and matures to be more potent and less deprivation-dependent by P12.
- These findings highlight the critical developmental window for the maturation of internal satiety signals.
Abstract:
The ontogenetic development of postingestive inhibitory control of ingestion by the osmotic load of a preload was examined in rats. On postnatal days 6 (P6) and 12 (P12), pups were deprived for either 6 or 24 h. Gastric preloads (5% body wt) of water, mannitol (a sugar alcohol that is not absorbed) in six concentrations [from 0.125 M (hypotonic) to 1.0 M (hypertonic)], or sham preloads were administered 5 min before a 30-min intake test. Compared with sham treatment, isotonic mannitol (0.25 M), a probe of volumetric control, significantly reduced intake on P12, but not on P6. Compared with isotonic mannitol, the three highest hypertonic concentrations (0.5, 0.66, and 1.0 M) significantly decreased intake on P12, at both levels of deprivation. On P6, 0.66 and 1.0 M mannitol reduced intake after 24 h, but not after 6 h, of deprivation. Thus, on P6, the hypertonic control was detectable only after prolonged deprivation and the volumetric control was not present. On P12, both controls were observed and the hypertonic control was more potent than on P6.