Hypertension in Prenatally Undernourished Young-Adult Rats Is Maintained by Tonic Reciprocal Paraventricular-Coerulear Excitatory Interactions

Abstract

Prenatally malnourished rats develop hypertension in adulthood, in part through increased alpha(1)-adrenoceptor-mediated outflow from the paraventricular nucleus (PVN) to the sympathetic system. We studied whether both alpha(1)-adrenoceptor-mediated noradrenergic excitatory pathways from the locus coeruleus (LC) to the PVN and their reciprocal excitatory CRFergic connections contribute to prenatal undernutrition-induced hypertension. For that purpose, we microinjected either alpha(1)-adrenoceptor or CRH receptor agonists and/or antagonists in the PVN or the LC, respectively. We also determined the alpha(1)-adrenoceptor density in whole hypothalamus and the expression levels of alpha(1A)-adrenoceptor mRNA in the PVN. The results showed that: (i) agonists microinjection increased systolic blood pressure and heart rate in normotensive eutrophic rats, but not in prenatally malnourished subjects; (ii) antagonists microinjection reduced hypertension and tachycardia in undernourished rats, but not in eutrophic controls; (iii) in undernourished animals, antagonist administration to one nuclei allowed the agonists recover full efficacy in the complementary nucleus, inducing hypertension and tachycardia; (iv) early undernutrition did not modify the number of alpha(1)-adrenoceptor binding sites in hypothalamus, but reduced the number of cells expressing alpha(1A)-adrenoceptor mRNA in the PVN. These results support the hypothesis that systolic pressure and heart rate are increased by tonic reciprocal paraventricular-coerulear excitatory interactions in prenatally undernourished young-adult rats.