Nitric Oxide Induced Heat Shock Protein 70 mRNA in Rat Hypothalamus during Acute Restraint Stress under Sucrose Diet

1. Sucrose feeding increases the level of stress-induced heat shock protein 70 mRNA in the rat hypothalamus. However, the mechanism by which a sucrose diet induces mRNA remains unclear. The issues investigated in this study were (1) whether a sucrose diet affects nitric oxide production in the hypothalamus, and (2) whether nitric oxide mediates the sucrose and stress-induced elevation of heat shock protein 70 mRNA. 2. To address the first question, we measured the level of nitrate, a final nitric-oxide-oxidation product measurable in vivo, using a microdialysis method. To address the second question, we administered a nitric oxide synthase inhibitor, N ^G-nitro-L-arginine methyl ester, prior to stress, then measured the mRNA level of heat shock protein 70 by the reverse transcription-competitive polymerase chain reaction method. 3. After the initiation of restraint stress, rats fed a sucrose-containing diet, unlike those fed standard chow, displayed a transient nitrate elevation. This nitrate elevation was attenuated by pretreatment with N^G-nitro-L-arginine methyl ester. The mRNA level increases in rats fed a sucrose diet were dose-dependently attenuated by N ^G-nitro-L-arginine methyl ester. 4. These data suggest that a sucrose diet induces heat shock protein 70 under stress by enhancing nitric oxide production in the hypothalamus.