The stimulatory effect of chronic lithium treatment on basal thyrotropin secretion in rats: In vivo antagonism by methylparaben

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dc.contributor.authorJaffer A.
dc.contributor.authorHarvey B.
dc.contributor.authorRussell V.A.
dc.contributor.authorCarstens M.E.
dc.contributor.authorDe Villiers A.S.
dc.contributor.authorTaljaard J.J.F.
dc.contributor.authorJaffer A.
dc.contributor.authorHarvey B.
dc.contributor.authorRussell V.A.
dc.contributor.authorCarstens M.E.
dc.contributor.authorDe Villiers A.S.
dc.contributor.authorTaljaard J.J.F.
dc.date.accessioned2011-05-15T16:17:26Z
dc.date.accessioned2011-05-15T16:17:26Z
dc.date.available2011-05-15T16:17:26Z
dc.date.available2011-05-15T16:17:26Z
dc.date.issued1993
dc.date.issued1993
dc.description.abstractChronic treatment of rats with lithium chloride was examined in order to determine its effect on hypothalamic monoamine and metabolite content, basal thyrotropin (TSH) secretion and thyroid function. The hypothalamic concentrations of noradrenaline (NA), dopamine (DA) and its metabolites, dihydroxyphenylacetic acid. (DOPAC) and homovanillic acid (HVA) in the lithium treated rats remained unaltered when compared to control levels. NA turnover and the NA metabolite, 3-methoxy-4-hydroxyphenylglycol (total MHPG), were significantly lower (p < 0.01), whereas both serotonin (5-HT) and its metabolite, 5-hydroxyindole-3-acetic acid (5-HIAA), were significantly higher (p < 0.01 and p < 0.02, respectively) in the lithium treated rat hypothalami than in controls. Chronic lithium treatment significantly elevated basal TSH levels (p < 0.05). This effect was antagonized by methyl p-hydroxybenzoate (methylparaben, p < 0.01), which did not itself affect basal TSH levels. Free serum T3 and T4 levels were not significantly affected by chronic lithium treatment, although T4 tended to be slightly lower than control levels. The monoamine changes observed in the hypothalamus of lithium treated rats did not appear to account for the elevated TSH levels observed in these rats since NA activity which is generally regarded as stimulatory was decreased and 5-HT which has an inhibitory effect on TSH secretion, was increased. The elevated TSH levels may have been due to a reduced negative feedback inhibition of TSH release by the mildly reduced circulating T4 levels caused by chronic lithium treatment. A further possibility is that the pituitary cGMP (and hence TSH) response to TRH may have been enhanced by chronic lithium treatment and methylparaben may have antagonized this effect.
dc.description.abstractChronic treatment of rats with lithium chloride was examined in order to determine its effect on hypothalamic monoamine and metabolite content, basal thyrotropin (TSH) secretion and thyroid function. The hypothalamic concentrations of noradrenaline (NA), dopamine (DA) and its metabolites, dihydroxyphenylacetic acid. (DOPAC) and homovanillic acid (HVA) in the lithium treated rats remained unaltered when compared to control levels. NA turnover and the NA metabolite, 3-methoxy-4-hydroxyphenylglycol (total MHPG), were significantly lower (p < 0.01), whereas both serotonin (5-HT) and its metabolite, 5-hydroxyindole-3-acetic acid (5-HIAA), were significantly higher (p < 0.01 and p < 0.02, respectively) in the lithium treated rat hypothalami than in controls. Chronic lithium treatment significantly elevated basal TSH levels (p < 0.05). This effect was antagonized by methyl p-hydroxybenzoate (methylparaben, p < 0.01), which did not itself affect basal TSH levels. Free serum T3 and T4 levels were not significantly affected by chronic lithium treatment, although T4 tended to be slightly lower than control levels. The monoamine changes observed in the hypothalamus of lithium treated rats did not appear to account for the elevated TSH levels observed in these rats since NA activity which is generally regarded as stimulatory was decreased and 5-HT which has an inhibitory effect on TSH secretion, was increased. The elevated TSH levels may have been due to a reduced negative feedback inhibition of TSH release by the mildly reduced circulating T4 levels caused by chronic lithium treatment. A further possibility is that the pituitary cGMP (and hence TSH) response to TRH may have been enhanced by chronic lithium treatment and methylparaben may have antagonized this effect.
dc.description.versionArticle
dc.description.versionArticle
dc.identifier.citationNeurochemical Research
dc.identifier.citation18
dc.identifier.citation10
dc.identifier.citationNeurochemical Research
dc.identifier.citation18
dc.identifier.citation10
dc.identifier.issn03643190
dc.identifier.issn03643190
dc.identifier.other10.1007/BF00966684
dc.identifier.other10.1007/BF00966684
dc.identifier.urihttp://hdl.handle.net/10019.1/14216
dc.identifier.urihttp://hdl.handle.net/10019.1/14216
dc.subjectcyclic amp; cyclic gmp; dopamine; homovanillic acid; liothyronine; lithium; lithium chloride; methyl paraben; noradrenalin; serotonin; thyrotropin; thyroxine; animal experiment; animal tissue; article; controlled study; depression; drug antagonism; hypothalamus; liothyronine blood level; male; mania; negative feedback; nonhuman; oral drug administration; priority journal; rat; thyroid function; thyrotropin blood level; thyrotropin release; thyroxine blood level; Animal; Dopamine; Hydroxyindoleacetic Acid; Hypothalamus; Lithium; Male; Methoxyhydroxyphenylglycol; Norepinephrine; Parabens; Protirelin; Rats; Rats, Wistar; Serotonin; Support, Non-U.S. Gov't; Thyrotropin; Thyroxine; Triiodothyronine; Animalia
dc.subjectcyclic amp
dc.subjectcyclic gmp
dc.subjectdopamine
dc.subjecthomovanillic acid
dc.subjectliothyronine
dc.subjectlithium
dc.subjectlithium chloride
dc.subjectmethyl paraben
dc.subjectnoradrenalin
dc.subjectserotonin
dc.subjectthyrotropin
dc.subjectthyroxine
dc.subjectanimal experiment
dc.subjectanimal tissue
dc.subjectarticle
dc.subjectcontrolled study
dc.subjectdepression
dc.subjectdrug antagonism
dc.subjecthypothalamus
dc.subjectliothyronine blood level
dc.subjectmale
dc.subjectmania
dc.subjectnegative feedback
dc.subjectnonhuman
dc.subjectoral drug administration
dc.subjectpriority journal
dc.subjectrat
dc.subjectthyroid function
dc.subjectthyrotropin blood level
dc.subjectthyrotropin release
dc.subjectthyroxine blood level
dc.subjectAnimal
dc.subjectDopamine
dc.subjectHydroxyindoleacetic Acid
dc.subjectHypothalamus
dc.subjectLithium
dc.subjectMale
dc.subjectMethoxyhydroxyphenylglycol
dc.subjectNorepinephrine
dc.subjectParabens
dc.subjectProtirelin
dc.subjectRats
dc.subjectRats, Wistar
dc.subjectSerotonin
dc.subjectSupport, Non-U.S. Gov't
dc.subjectThyrotropin
dc.subjectThyroxine
dc.subjectTriiodothyronine
dc.subjectAnimalia
dc.titleThe stimulatory effect of chronic lithium treatment on basal thyrotropin secretion in rats: In vivo antagonism by methylparaben
dc.titleThe stimulatory effect of chronic lithium treatment on basal thyrotropin secretion in rats: In vivo antagonism by methylparaben
dc.typeArticle
dc.typeArticle
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