Central neuropeptide Y stimulates ingestive behavior and increases urine output in the ovine fetus

Abstract

We hypothesized that central neuropeptide Y (NPY) increases swallowing activity and alters renal function in the near-term ovine fetus. Six ewes with singleton fetuses (130 ± 2 days of gestation; 148 days = term) were chronically prepared with arterial and venous catheters, a fetal lateral cerebroventricular cannula, and fetal bladder and amniotic fluid catheters. For determination of fetal swallowing, electromyogram wires were placed in the fetal thyrohyoid muscle and the upper and lower nuchal esophagus. Electrodes were implanted on the parietal dura for determination of fetal electrocorticogram (ECoG). After 5 days of recovery, fetal swallowing, ECoG, blood pressure, and heart rate were monitored during a 3-h basal period. At t = 3 h, ovine NPY (0.05 mg/kg) was administered into the lateral ventricle, and fetuses were monitored for an additional 8 h. A control study of central administration of artificial cerebral spinal fluid was performed on an alternate day. Central NPY significantly increased swallowing activity during low-voltage ECoG from basal activity (1.26 ± 0.15 swallows/min) at 4 h (1.93 ± 0.37 swallows/min), 6 h (1.69 ± 0.27 swallows/ min), and 8 h (2.38 ± 0.31 swallows/min). NPY significantly increased fetal urine flow (basal: 0.13 ± 0.02; 4 h: 0.21 ± 0.04; 6 h: 0.19 ± 0.03 ml · kg-1 · min-1). These results demonstrate that central NPY stimulates fetal swallowing activity and increases urine output, which may contribute to the in utero development of ingestive behavior.