Unopposed appetite (orexigenic) mechanisms in the near-term ovine fetus: central leptin does not inhibit sucrose ingestion.
OBJECTIVE
Leptin is produced in adipocytes and is present in the term fetus. In the adult, leptin acts centrally to inhibit neuropeptide Y-induced carbohydrate intake. We sought to examine if central leptin alters fetal ingestion of oral sucrose in the near-term ovine fetus.


METHODS
Five pregnant ewes and fetuses were prepared with fetal vascular, sublingual and intracerebroventricular (ICV) catheters and esophageal electromyogram electrodes, and studied at 132 +/- 1 days' gestation (term 145-150 days). Following a 2-h baseline period, 10% sucrose was infused sublingually (0.25 ml/min) for the duration of the study. At time 4 h, leptin (0.075 mg/kg) was administered ICV and fetal swallowing was monitored for an additional 6 h.


RESULTS
During the basal period, fetal swallowing averaged 0.7 +/- 0.1 swallows/min. Fetal swallowing increased significantly in response to 10% sucrose (1.2 +/- 0.1 swallows/min; p < 0.05). In response to ICV leptin, fetal swallowing remained significantly elevated at 2, 4 and 6 h (1.3 +/- 0.4, 1.4 +/- 0.3 and 1.5 +/- 0.2 swallows/min, respectively; p < 0.05 vs. control).


CONCLUSIONS
These results indicate that central leptin inhibition of sucrose ingestion is not functional in the near-term fetus. We speculate that a leptin-mediated anorexigenic response is not present at birth, such that unopposed appetite stimulatory mechanisms in the newborn may facilitate rapid newborn weight gain despite high body fat levels.
El-Haddad
M A
MA
Perinatal Research Laboratories, David Geffen School of Medicine, University of California at Los Angeles, California, USA.
Ismail
Y
Y
Day
L
L
Ross
M  G
M
D000286:Administration, Sublingual; D000818:Animals; D003679:Deglutition / Q000187:drug effects / Q000502:physiology; D004576:Electromyography; D004947:Esophagus / Q000187:drug effects* / Q000196:embryology / Q000502:physiology*; D005260:Female; D005333:Fetus / Q000502:physiology*; D007276:Injections, Intraventricular; D020738:Leptin / Q000008:administration & dosage / Q000494:pharmacology*; D011247:Pregnancy; D012756:Sheep; D013395:Sucrose / Q000008:administration & dosage / Q000494:pharmacology*
D020738:Leptin; D013395:Sucrose