Neuroendocrine mechanisms of change in food intake during pregnancy: a potential role for brain oxytocin.

During pregnancy body weight, and particularly adiposity, increase, due to hyperphagia rather than decreased energy metabolism. These physiological adaptations provide the growing fetus(es) with nutrition and prepare the mother for the metabolically-demanding lactation period following birth. Mechanisms underlying the hyperphagia are still poorly understood.

Neuronal activation in the hypothalamus and brainstem during feeding in rats.

We trained rats to a regime of scheduled feeding, in which food was available for only 2 hr each day. After 10 days, rats were euthanized at defined times relative to food availability, and their brains were analyzed to map Fos expression in neuronal populations to test the hypothesis that some populations are activated by hunger whereas others are activated by satiety signals. Fos expression accompanied feeding in several hypothalamic and brainstem nuclei.

Hypothalamic expression of NPY mRNA, vasopressin mRNA and CRF mRNA in response to food restriction and central administration of the orexigenic peptide GHRP-6.

In this study, we examined the effects of restricted feeding and of central administration of an orexigenic ghrelin agonist GHRP-6 on peptide mRNA expression in the hypothalamus. We compared rats fed ad libitum with rats that were allowed food for only 2?h every day, and treated with a continuous chronic i.c.

Actions of neuropeptide Y and growth hormone secretagogues in the arcuate nucleus and ventromedial hypothalamic nucleus.

Systemic or central administration of growth-hormone secretagogues (GHS) induces dense Fos expression in the arcuate nucleus but little or no Fos expression in the ventromedial hypothalamic nucleus, although both sites show intense expression of mRNA for the GHS receptor. Here, we recorded the electrical activity of single neurons from the arcuate nucleus and from the ventromedial hypothalamic nucleus in a rat hypothalamic slice preparation, and compared responses of these two populations to GHS. At both sites, the predominant neuronal response to GHS was a long-lasting excitation, indicating that GHS receptors at both sites are functional and similarly coupled to electrical excitation.