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Inhibition of Hypothalamic Nitric Oxide Synthase Gene Expression in the Rat Paraventricular Nucleus by Food Deprivation is Independent of Serotonin Depletion
Author(s) -
Ueta Yoichi,
Levy Andrew,
Chowdrey Hardial S.,
Lightman Stafford L.
Publication year - 1995
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.1995.tb00727.x
Subject(s) - endocrinology , medicine , nitric oxide synthase , serotonin , nucleus , hypothalamus , chemistry , gene expression , nitric oxide , biology , gene , neuroscience , biochemistry , receptor
We have investigated the effects of food deprivation on nitric oxide synthase (NOS) transcript levels in the rat paraventricular (PVN) and supraoptic nuclei (SON), using in situ hybridization histochemistry. Food deprivation for 48 h significantly and consistently reduced NOS transcript prevalence by approximately 50% in both sites. Since there is considerable evidence for an important role of 5‐HT in feeding behaviour, we then examined the effect of food deprivation on NOS gene expression in the PVN following para ‐chlorophenylalanine (PCPA)‐induced hypothalamic 5‐HT depletion. As starvation causes central down‐regulation of the thyroid axis, changes in thyrotropinreleasing hormone (TRH) and pituitary thyrotrophin (TSH) transcript prevalence were used as internal controls. PCPA pretreatment (200 mg/kg body weight as a single daily dose ip for 2 days) had no significant effect on basal levels of NOS, TRH or TSH transcripts, or on the effect of a subsequent 48 h fast, which significantly reduced all three. These results show for the first time, that food deprivation for 48 h significantly reduces NOS gene expression in the rat PVN and SON. Secondly, that basal levels and the fasting‐induced reductions in the prevalence of NOS, TRH and TSH transcripts were not affected by PCPA‐induced hypothalamic 5‐HT depletion. Therefore, at least under the experimental conditions used here, 5‐HT does not appear to be involved in setting baseline levels—or in the starvation‐induced inhibition of NOS or thyroid axis gene expression in the PVN.