Aberrant Monoaminergic System in Thyroid Hormone Receptor-ß Deficient Mice as a Model of Attention-Deficit/Hyperactivity Disorder.

BACKGROUND: Thyroid hormone receptors are divided into 2 functional types: TRα and TRß. Thyroid hormone receptors play pivotal roles in the developing brain, and disruption of thyroid hormone receptors can produce permanent behavioral abnormality in animal models and humans. METHODS: Here we examined behavioralchanges, regional monoamine metabolism, and expression of epigenetic modulatory proteins, including acetylated histone H3 and histone deacetylase, in the developing brain of TRα-disrupted (TRα (0/0) ) and TRß-deficient (TRß (-/-) ) mice. Tissue concentrations of dopamine, serotonin (5-hydroxytryptamine) and their metabolites in the mesocorticolimbic pathway were measured. RESULTS: TRß (-/-) mice, a model of attention-deficit/hyperactivity disorder, showed significantly high exploratory activity and reduced habituation, whereas TRα (0/0) mice showed normal exploratory activity. The biochemical profiles of dopamine and 5-hydroxytryptamine showed significantly low dopamine metabolic rates in the caudate putamen and nucleus accumbens and overall low 5-hydroxytryptamine metabolic rates in TRß (-/-) mice, but not in TRα (0/0) mice. Furthermore, the expression of acetylated histone H3 was low in the dorsal raphe of TRß (-/-) mice, and histone deacetylase 2/3 proteins were widely increased in the mesolimbic system. CONCLUSIONS: These findings suggest that TRß deficiency causes dysfunction of the monoaminergic system, accompanied by epigenetic disruption during the brain maturation process.

Antidepressants and mood stabilizers effects on histone deacetylase expression in C57BL/6 mice: Brain region specific changes.

To determine whether treatment with various antidepressants or mood stabilizers leads to region-specific changes, we investigated the effects of their subchronic (14 days of intraperitoneal injection) administration on the tissue concentration of monoamines, dopamine, serotonin, and norepinephrine, and the protein expression of acetylated histone H3 (AcH3) and histone deacetylases (HDACs) in the mouse striatum (ST), nucleus accumbens (Acb), hippocampus (Hip), cingulate cortex (Cg), and amygdala (Amy). Subchronic administration with the antidepressants (S)-citalopram oxalate (ECM), duloxetine hydrochloride (DLX), and mirtazapine (MIR) commonly induced significant increases in dopamine and serotonin levels in the ST and Cg. By contrast, no common profiles for dopamine, serotonin, or norepinephrine were identified in the Acb, Hip, or Amy. Treatment with sodium valproate (VPA), lithium chloride (Li), lamotrigine (LTG), levetiracetam (LTM), olanzapine (OLZ), clozapine (CLZ), clomipramine (CLM), ECM, and DLX induced significant increases in AcH3 expression in the Acb, while treatment with CLM, ECM, DLX, MIR, carbamazepine (CBZ), LTG, LTM, OLZ, or CLZ induced significant increases in HDAC2 and HDAC3 in the ST. CLM, MIR, VPA, CBZ, LTG, LTM, OLZ, or CLZ induced significant increases in HDAC3 in the Cg, and ECM, DLX, MIR, VPA, CBZ, LTG, LTM, or OLZ resulted in significant increases in HDAC5 in the Amy. Collectively, the changes of monoamine content were restricted for mood stabilizer effects, but increased expression of HDAC2, HDAC3, or HDAC5 in the ST, Cg, or Amy was often found, supporting the possibility that antidepressant-like effects involve epigenetic modifications associated with changes in HDAC expression.

Gender differences on MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) neurotoxicity in C57BL/6 mice.

The aim of this study was to investigate the impact of gender difference in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated animal model of Parkinson's disease (PD). In the present study, we investigated the time-dependent alterations of dopamine and its metabolites, striatal tyrosine hydroxylase (TH) protein, dopamine transporter (DAT) protein, glial fibrillary acidic protein (GFAP) protein and midbrain TH protein and motor function in male and female mice 5h and 1, 3 and 7 days after four administrations of MPTP (20mg/kg) at 2-h intervals. The present study showed that the decrease of dopamine, DOPAC (3,4-dihydroxyphenylacetic acid) and HVA (homovanillic acid) content in female mice was more pronounced than that in male animals 1, 3 and 7 days after MPTP treatment. Our Western blot analysis study also demonstrated that the decrease of both striatal and midbrain TH protein levels in female mice was more pronounced than that in male animals from 1 to 7 days after MPTP treatment. As compared to male mice, in contrast, the increase of striatal GFAP protein levels in female mice was observed from 5h to 7 days after MPTP treatment. Furthermore, the present study showed that motor deficits were found in both male and female mice 1 and 7 days after MPTP treatment. In the present study, moreover, the decrease of striatal DAT protein levels in female mice was more pronounced than that in male animals 1, 3 and 7 days after MPTP treatment. These results demonstrate that our administrations of MPTP at 2-h intervals can cause more severe damage in female mice as compared with male animals. The gender difference may be due to the decrease of DAT expression caused by MPTP. Thus our findings provide further valuable information for the pathogenesis of PD.

Effects of estrogens on striatal damage after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity in male and female mice.

Emerging evidence shows a beneficial effect of estrogens for Parkinson's disease, yet the exact potency of these compounds implicated remain obscured. In this study, we investigated the neuroprotective effect of 17beta-estradiol and estrone against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced striatal toxicity in mice. The neuroprotective effects of both compounds were evaluated by HPLC and Western blot analyses 5 days after the last of 4 consecutive injections of MPTP at 1-h intervals to mice. Subacute treatment (10 days) with estrone or 17beta-estradiol at low doses (0.05 and 0.2mg/kg) showed no significant changes against MPTP-induced damage of striatal dopamine terminals in mice. Furthermore, acute treatment with estrone at high doses (0.5 and 2.0mg/kg) showed no significant alterations against MPTP-induced damage of striatal dopamine terminals in mice. In contrast, acute treatment with 17beta-estradiol at high doses exhibited a neuroprotective effect against the damage of striatal dopamine terminals in both male and female mice after MPTP treatments. The results demonstrate that estrogen therapy with high doses may have a neuroprotective effect on the damage of striatal dopamine terminals in the MPTP-induced mice. These findings may lead to be development of estrogen therapy for the prevention and treatment of Parkinson's disease.