Region-specific effects of hypothyroidism on the relative expression of thyroid hormone receptors in adult rat brain.

The aim of this study was to determine whether changes in the circulating thyroid hormone (TH) and brain synaptosomal TH content affected the relative levels of mRNA encoding different thyroid hormone receptor (TR) isoforms in adult rat brain. Northern analysis of polyA+RNA from cerebral cortex, hippocampus and cerebellum of control and hypothyroid adult rats was performed in order to determine the relative expression of all TR isoforms. Circulating and synaptosomal TH concentrations were determined by radioimmunoassay.

The effect of chloral hydrate on the in-vitro T3 binding to adult rat cerebral nuclei.

Chloral hydrate is a widely used hypnotic drug for children and animals but the possible interactions of its sedative action and thyroid hormones has not been investigated. In this study the effect of chloral hydrate on the in-vitro binding of triiodothyronine (T3) to cerebral nuclei of adult rats and on the thyroid hormones' synaptosomal and plasma availability were examined. Our results show that during deep anaesthesia caused by a single intraperitoneal administration of chloral hydrate (100 mg kg(-1)), the maximal number of nuclear thyroid hormone receptors (Bmax) and the equilibrium dissociation constant (Kd) were decreased.

Diazepam affects the nuclear thyroid hormone receptor density and their expression levels in adult rat brain.

Thyroid hormones (THs) are involved in the occurrence of anxiety and affective disorders; however, the effects following an anxiolytic benzodiazepine treatment, such as diazepam administration, on the mechanism of action of thyroid hormones has not yet been investigated. The effect of diazepam on the in vitro nuclear T3 binding, on the relative expression of the TH receptors (TRs) and on the synaptosomal TH availability were examined in adult rat cerebral hemispheres 24 h after a single intraperitoneal dose (5 mg/kg BW) of this tranquillizer. Although, diazepam did not affect the availability of TH either in blood circulation or in the synaptosomal fraction, it decreased (33%) the nuclear T3 maximal binding density (B(max)).

Pentylenetetrazole-induced convulsions affect cellular and molecular parameters of the mechanism of action of triiodothyronine in adult rat brain.

The aim of the current study was to elucidate whether the response of the adult rat brain to thyroid hormones is affected by the intensity of neuronal activity. For this purpose, the kinetic characteristics of nuclear T3 binding, the relative expression of thyroid hormone receptor (TR) isoforms and the synaptosomal content of thyroid hormones in adult rat brain were examined after administration of a single convulsion dose of pentylenetetrazole (PTZ). Experiments in adult Wistar rats revealed an increase (33%) of the density of specific T3 nuclear receptors in cerebral hemispheres 4h after PTZ-induced seizures while no changes were observed in the dissociation constant.

Acute LiCl-treatment affects the cytoplasmic T4 availability and the expression pattern of thyroid hormone receptors in adult rat cerebral hemispheres.

We have previously reported that short-term LiCl-treatment affects the kinetic characteristics of thyroid hormone binding in adult rat brain (Bolaris, S., Margarity, M., Valcana, T.