Synaptosomal T3 Content in Cerebral Cortex of Adult Rat in Different Thyroidal States

Abstract

Although high affinity, low capacity nuclear thyroid hormone receptors have been localized in the adult rat brain, no physiological parameter has been identified that may be accepted as an expression of the thyroid hormone-receptor interaction in this organ (Eberhardt et al. 1978;Schwartz and Oppenheimer 1978;Valcana and Timiras 1978;Dozin-Van Roye and De Nayer 1979;Oppenheimer et al. 1980; Gullo et al. 1987a,b). Recent evidences have shown selective uptake of thyroxine (T4) and triiodothyronine (T3), rapid conversion of T4 to T3, and specific 125 l-T3-binding sites in synaptosomal fraction of nervous tissue in the adult rat brain. This favors direct nonnuclear action of thyroid hormone related to neurotransmission in the adult mammalian brain (Dratman et al. 1976

Maintenance of Homeostasis for Thyroid Hormone in the Adult Rat Brain: Possible Involvement of a Nuclear-Mediated Phenomenon

“…However, the T 4 level was undetectable, similar to our previous findings [4, 19]. This might be due to the rapid conversion of brain T 4 to T 3 by the PTU-insensitive DII [3, 5].…”

l-Triiodothyronine differentially and nongenomically regulates synaptosomal protein phosphorylation in adult rat brain cerebral cortex: Role of calcium and calmodulin

“…The 40 µM concentration of KN62 completely blocked the effect of Ca 2+ /CaM-dependent phosphorylation of 63-and 53-kD proteins induced by L-T3 (lane 11). This enhancement of Ca 2+ /CaM-dependent protein phosphorylation by brain physiological concentrations of L-T3 (10 nM) (Sarkar and Ray, 1994) suggested the involvement of CaMK-II in regulating the phosphorylation of 63-and 53-kD proteins. A. L-T3-stimulated phosphorylation of 63-and 53-kD proteins is regulated by Ca 2+ / CaM-dependent protein kinase II.…”

“…This concentration of L-T3 (10 nM) was determined from the dose-response curve (Fig. 1) and was considered to be within the brain physiological concentration of L-T3 in adult rat synaptosomes as we previously reported (Sarkar and Ray, 1994). Corresponding silver-stained protein bands in Fig.…”

“…Recent ongoing search on biochemical characterization and unveiling of the important steps of the signaling pathways to understand the molecular basis of the nontranscriptional mechanism of action of TH that leads to physiologic functions are fascinating (Hiroi et al, 2006;Flamant et al, 2007). We have also shown varied levels of THs in adult rat brain cerebrocortical synaptosomes in different thyroid conditions (Sarkar and Ray, 1994). L-T3 also has been shown to regulate intracellular calcium (Ca 2+ ) levels in adult rat brain synaptosomes (Mason et al, 1990;Chakrabarti and Ray, 2000;Sarkar and Ray, 2003), in hypothyroid mouse cerebral cortex (Iqbal et al, 2002), and in single rat myocytes (Lomax et al, 1991) rapidly and nongenomically.…”

Thyroid hormones and the treatment of depression: An examination of basic hormonal actions in the mature mammalian brain

“…Evidence for this hypothesis includes the demonstration of a selective uptake of [ 125 I]T 3 into synaptosomes (Dratman et al, 1976;Dratman and Crutchfield, 1978;Kastellakis and Valcana, 1989), localization of specific T 3 receptors in the synaptic membrane (Mashio et al, 1982(Mashio et al, , 1983, inhibition of the uptake of gamma-aminobutyric acid (GABA) into synaptosomes in a manner that excludes a shared transport mechanism (Mason et al, 1987b,c), T 3 -mediated enhancement of depolarization-induced uptake of Ca 11 (Mason et al, 1990), release of T 3 from synaptosomes via Ca 11 -dependent depolarization (Mason et al, 1993), a 9-fold increase in synaptosomal T 3 concentrations during hypothyroidism (Sarkar and Ray, 1994), the possible conversion of T 4 to T 3 within nerve terminals (Dratman and Crutchfield, 1978), and a nonuniform distribution of exogenously administered T 3 within the CNS (Dratman et al, 1982a(Dratman et al, , 1987Dratman and Crutchfield, 1989). Limited evidence relative to the physiological importance of these findings has been provided (Dratman et al, 1982b).…”