Depolarization-dependent sup 45 Ca uptake by synaptosomes of rat cerebral cortex is enhanced by L-triiodothyronine

Journal Article · Wed Aug 01 04:00:00 EDT 1990 · Neuropsychopharmacology; (USA)

OSTI ID:6423022

Mason, G A; Walker, C H; Prange, Jr, A J ^[1]

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1. Univ. of North Carolina, Chapel Hill (USA)

Depolarization-induced release of neurotransmitters and other secretions from nerve endings is triggered by the rapid entry of Ca++ through voltage-sensitive channels. Calcium entry is thought to occur in two distinct phases or processes: a fast-phase response to an action potential, which initiates release; and a slow phase associated with extended stimulation of the neuron. Thyroid hormones are sequestered by nerve terminals and can produce changes in behaviour and mood. They may therefore be involved in modulating central synaptic transmission. We studied the effects of L-triiodothyronine (T3), L-thyroxine (T4), reverse T3 (rT3) and D-T3 on depolarization-induced uptake of 45Ca by synaptosomes from euthyroid and hypothyroid rats. T3, but not T4, rT3, or D-T3 significantly enhanced depolarization-induced 45Ca uptake at physiologically relevant (1 to 10 nmol/L) concentrations. The stimulatory effect of 10 nmol/L T3 on depolarization-induced uptake after 2 seconds (21%) was greater than after 5 (10%) or 30 (8%) seconds, indicating that T3 enhanced primarily the fast-phase process. There was no effect of T3 or other hormones tested on nondepolarization-induced 45Ca uptake. Preincubation of synaptosomes with T3 prior to depolarization did not enhance the effect of T3; in fact, preincubations of 30 seconds or more resulted in diminished T3 effects. Preincubation of synaptosomes for 15 seconds with D-T3 or the addition of D-T3 and T3 together reduced the effect of T3. We found no difference in the effect of T3 on 45Ca uptake by synaptosomes from euthyroid and hypothyroid rats. These results suggest a novel mechanism of action of thyroid hormones in the brain.

• OSTI ID: 6423022
• Journal Information: Neuropsychopharmacology; (USA), Journal Name: Neuropsychopharmacology; (USA) Vol. 3:4; ISSN NEROE; ISSN 0893-133X
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
AMINO ACIDS
ANIMAL CELLS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOELECTRICITY
BODY
BRAIN
CALCIUM 45
CALCIUM COMPOUNDS
CALCIUM ISOTOPES
CARBOXYLIC ACIDS
CENTRAL NERVOUS SYSTEM
DAYS LIVING RADIOISOTOPES
ELECTRICITY
EVEN-ODD NUCLEI
HORMONES
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MAMMALS
MEMBRANE TRANSPORT
NERVE CELLS
NERVOUS SYSTEM
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC IODINE COMPOUNDS
ORGANS
PEPTIDE HORMONES
RADIOISOTOPES
RATS
REACTION KINETICS
RODENTS
SOMATIC CELLS
THYROID HORMONES
THYROXINE
TRACER TECHNIQUES
TRIIODOTHYRONINE
VERTEBRATES