Refeeding-induced expression of neuronal nitric oxide synthase in the rat paraventricular nucleus.
We have previously reported that food deprivation decreases the expression of neuronal nitric oxide synthase (nNOS) in the hypothalamic paraventricular nucleus (PVN) of rats, and this reduction is inhibited by blockade of glucocorticoid receptors. In this study, we examined whether the fasting-induced decrease in nNOS gene expression in the PVN is restored by refeeding. The number of nNOS immunopositive cells in the PVN, which was markedly decreased by 48 h of food deprivation, increased significantly after 6 h of refeeding and was fully restored by 24 h after refeeding. The plasma corticosterone level, which was markedly increased by food deprivation, decreased significantly within 30 min after refeeding and returned to the free fed control level by 6 h. Synthetic glucocorticoid dexamethasone blocked the refeeding-induced nNOS expression in the PVN without suppressing food intake. Refeeding with a non-caloric food mash for 5 h failed to restore the fasting-induced decrease in the PVN-nNOS but did, however, successfully restore the plasma corticosterone level. These results suggest that the refeeding-induced nNOS expression in the PVN is a nutrient-directed event and that plasma glucocorticoids may play an inhibitory role in the regulatory pathway. Additionally, glucocorticoid disinhibition alone does not appear to be sufficient to induce nNOS expression in the PVN; nNOS expression in the PVN upon refeeding may require both nutrient supplementation and glucocorticoid disinhibition.
Jahng
Jeong Won
JW
Department of Pharmacology, BK21 project for Medical Science, Yonsei University College of Medicine, Seoul 120-752, South Korea. jwjahng@yumc.yonsei.ac.kr
Lee
Joo Young
JY
Yoo
Sang Bae
SB
Kim
Yun Mi
YM
Ryu
Vitaly
V
Kang
Dong Won
DW
Lee
Jong-Ho
JH
D000704:Analysis of Variance; D000818:Animals; D000932:Antiemetics / Q000494:pharmacology; D001522:Behavior, Animal; D003345:Corticosterone / Q000097:blood; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D005247:Feeding Behavior / Q000187:drug effects / Q000502:physiology*; D005508:Food Deprivation / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology*; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000201:enzymology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D000932:Antiemetics; D017362:Cyclic AMP Response Element-Binding Protein; D009419:Nerve Tissue Proteins; D003907:Dexamethasone; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; D003345:Corticosterone