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Pharmaco-ontogenic modulation of feeding by oxytocin, bombesin, and their antagonists
1School of Psychology, University of Ottawa, Ontario, Canada. merali@uottawa.ca
Abstract:
Oxytocin (OX) and bombesin (BN) can both suppress food intake in adult rats. In light of important transient fluctuations in peptide and/or receptor expression early after birth, this study characterized the feeding-suppressant effects of OX and BN during early development and explored their physiological relevance, using BN or OX antagonists, [D-Phe6,des-Met6-14]BN(6-14), ethyl amide (des-Met), and [des-Glycinamide9,d(CH2)5',O-Me-Tyr2,Thr4,Orn8]-vaso toc in (vasotocin), respectively. On postnatal days (PD) 1, 5, 10, and 15, groups of food-deprived Sprague-Dawley rat pups (n = 8-11) were injected SC with saline (control) or BN (0.6, 0.06, or 0.006 mg/kg), des-Met (10 mg/kg), OX (1.2, 0.6, 0.3, or 0.15 mg/kg), or vasotocin (1.0 mg/kg), and their intake of milk (from a piece of absorbent paper saturated with warm milk) was monitored. Results revealed that BN and OX suppressed milk intake from PD 1 to PD 15. Although the milk intake varied with the peptide dose, this effect was age dependent. The doses of BN (but not OX) required to suppress feeding were higher than those needed in adults. When administered alone, OX or BN antagonists did not affect food intake, except at PD 15 for des-Met and PD 1 and PD 10 for vasotocin, where they enhanced feeding. These results suggest that pharmacological effects to OX and BN are apparent from hours after birth and that these peptides may play a role in the regulation of ingestive behavior from early on in ontogeny.
Insights
Oxytocin and bombesin suppress milk intake in developing rats from birth. These peptides may regulate feeding behavior early in life, with effects observed shortly after birth.
Area of Science:
- Neuroscience
- Developmental Biology
- Endocrinology
Background:
- Oxytocin (OX) and bombesin (BN) are known to suppress food intake in adult rats.
- Fluctuations in peptide and receptor expression occur early in development.
- The role of these peptides in early-life feeding regulation is not well understood.
Purpose of the Study:
- To characterize the feeding-suppressant effects of OX and BN in developing rats.
- To explore the physiological relevance of OX and BN in early ingestive behavior.
- To investigate the effects of OX and BN antagonists on food intake during development.
Main Methods:
- Sprague-Dawley rat pups were studied on postnatal days (PD) 1, 5, 10, and 15.
- Pups received subcutaneous injections of saline, BN, OX, or their respective antagonists (des-Met for BN, vasotocin for OX).
- Milk intake was monitored after injections in food-deprived pups.
Main Results:
- Both BN and OX suppressed milk intake in rat pups from PD 1 to PD 15.
- The feeding-suppressant effects were dose- and age-dependent.
- BN required higher doses than OX to suppress feeding, and doses were higher than in adults.
Conclusions:
- Pharmacological effects of OX and BN on feeding are evident from hours after birth.
- These peptides likely play a significant role in regulating ingestive behavior early in ontogeny.
- Antagonists showed some effects on feeding, particularly at specific developmental stages.