Persistent sucrose stimulation of ovine fetal ingestion: lack of adaptation responses.
OBJECTIVE
Sweet taste responsiveness is reduced in adult rats and humans following continued oral sucrose. We have previously demonstrated that sublingual sucrose stimulates near term ovine fetal swallowing, suggesting intact taste responsiveness. We sought to determine if prolonged oral sucrose infusion to the near term ovine fetus will evoke adaptation, as manifested by reduced swallowing stimulation.


METHODS
Time-dated pregnant ewes and fetuses (n = 4) were chronically prepared with fetal vascular and sublingual catheters, and electrocorticogram and esophageal electromyogram electrodes and studied at 129 +/- 1 d gestation. Following an initial 2 h basal period, sucrose (2.5%) was infused sublingually (0.25 ml/min) to the fetus for 8 h. Fetal swallowing activity, blood pressure and heart rate were continuously recorded while maternal and fetal arterial blood samples were taken at timed intervals.


RESULTS
During the basal period, fetal swallowing averaged 0.9 +/- 0.1 swallows/min. Fetal swallowing increased significantly following sublingual 2.5% sucrose infusion and remained significantly elevated at 2, 4, 6 and 8 h after initiation of sucrose infusion (1.3 +/- 0.1, 1.2 +/- 0.1, 1.3 +/- 0.1, 1.3 +/- 0.1 swallows/min; p < 0.001). There were no significant changes in fetal cardiovascular or arterial blood parameters.


CONCLUSIONS
Although oral sucrose significantly stimulates near term ovine fetal ingestive behavior, sweet taste adaptation or habituation does not occur, in contrast to that observed in adult animals and human. The lack of taste adaptation in the fetus/newborn may facilitate increased neonatal food intake and accelerated growth.
El-Haddad
Mostafa A
MA
Perinatal Research Laboratories, Department of Obstetrics and Gynecology, Geffen School of Medicine at UCLA, Harbor-UCLA Medical Center, Torrance, California, USA. mostafa.elhaddad@cox.net
Jia
Yousheng
Y
Ross
Michael G
MG
D000222:Adaptation, Physiological; D000286:Administration, Sublingual; D000818:Animals; D001784:Blood Gas Analysis; D001794:Blood Pressure; D003679:Deglutition / Q000187:drug effects* / Q000502:physiology; D004576:Electromyography; D004947:Esophagus / Q000502:physiology; D005260:Female; D005333:Fetus / Q000502:physiology*; D006339:Heart Rate; D011247:Pregnancy; D012756:Sheep; D013268:Stimulation, Chemical; D013395:Sucrose / Q000008:administration & dosage*
D013395:Sucrose