A putative role for hypothalamic glucocorticoid receptors in hypertension induced by prenatal undernutrition in the rat.

Prenatal undernutrition induces hypertension later in life, possibly by disturbing the hypothalamo-pituitary-adrenal axis through programming decreased expression of hypothalamic glucocorticoid receptors. We examined the systolic blood pressure, heart rate and plasma corticosterone response to intra-paraventricular dexamethasone, mifepristone and corticosterone in eutrophic and prenatally undernourished young rats. Undernutrition was induced during fetal life by restricting the diet of pregnant mothers to 10 g daily (40% of diet consumed by well-nourished controls). At day 40 of postnatal life (i) intra-paraventricular administration of dexamethasone significantly reduced at least for 24h both the systolic pressure (-11.6%), the heart rate (-20.8%) and the plasma corticosterone (-40.0%) in normal animals, while producing lower effects (-5.5, -8.7, and -22.3%, respectively) on undernourished rats; (ii) intra-paraventricular administration of the antiglucocorticoid receptor ligand mifepristone to normal rats produced opposite effects (8.2, 20.3, and 48.0% increase, respectively) to those induced by dexamethasone, being these not significant in undernourished animals; (iii) intra-paraventricular corticosterone did not exert any significant effect. Results suggest that the low sensitivity of paraventricular neurons to glucocorticoid receptor ligands observed in prenatally undernourished rats could be due to the already reported glucocorticoid receptor expression, found in the hypothalamus of undernourished animals.

Fetal undernutrition induces overexpression of CRH mRNA and CRH protein in hypothalamus and increases CRH and corticosterone in plasma during postnatal life in the rat.

Prenatal undernutrition induces a variety of cardiovascular alterations in mammals when adults, including hypertension and hypercortisolism, which are thought to be caused by decreased glucocorticoid feedback control of the hypothalamus-pituitary-adrenal (HPA) axis programmed during fetal life. Hypothalamic CRH seems to be involved in blood pressure elevation of spontaneously hypertensive rats and in primary hypertension of humans, but the influence of prenatal undernutrition on CRH expression has deserved little attention. Here, we studied the expression of both CRH mRNA and CRH protein in the hypothalamus of neonatal and juvenile offspring of rats undernourished during fetal life, as well as the plasma levels of CRH and corticosterone. Prenatal undernutrition of pups was induced by submitting pregnant rats to diet restriction (10g daily of 21% protein standard laboratory diet). Pups born from dams with free access to the standard laboratory diet served as controls. At day 2 of postnatal age, undernourished pups showed lower body and brain weights, but higher plasma CRH and corticosterone than normal pups. At day 40 of age, brain weight was significantly decreased in the undernourished rats, while plasma corticosterone, plasma CRH and systolic pressure were significantly increased in these animals. At days 2 and 40 of postnatal age, increased CRH mRNA expression and CRH concentration were found in the hypothalamus of undernourished rats. Results indicate that, in the rat, prenatal undernutrition led to fetal programming of CRH overexpression, a neuropeptide serving as activating signal to the HPA axis and/or to extrahypothalamic brain regions concerned with cardiovascular regulation.

Prenatal malnutrition-induced hypertension in young rats is prevented by neonatal capsaicin treatment.

Prenatal malnutrition-induced fetal growth retardation in the rat results in elevated arterial blood pressure at adulthood. To test the contribution of cardiovascular sensory C fibers in the hypertensive state, arterial blood pressure was measured in prenatally undernourished rats treated at birth with capsaicin. The effects of the neonatal capsaicin treatment on heart rate and respiratory frequency were also evaluated. Maternal malnutrition resulted in body and brain weights deficits in the offspring that were not modified by neonatal capsaicin treatment. Capsaicin treatment did not change the cardiovascular parameters in normal rats, but prevented the elevation of arterial blood pressure and heart rate in malnourished animals. These results indicate that elevation of arterial blood pressure in prenatally malnourished rats depends on the activity of some sensory unmyelinated C fibers.