The effects of thyroid hormones on potassium-stimulated release of 3H-GABA by synaptosomes of rat cerebral cortex.
Depolarization-induced release of neurotransmitters from nerve endings is triggered by the rapid entry of Ca through voltage-sensitive channels. Low (1 to 10 nmol/L) concentrations of L-triiodothyronine (T3), but not D-T3, reverse T3 (rT3) or L-thyroxine (T4), enhance fast-phase depolarization-induced 45Ca uptake by rat brain synaptosomes. In the present study the effects of thyroid hormones on the release of 3H-gamma-aminobutyric acid (3H-GABA) by cerebral cortical synaptosomes from adult male Sprague-Dawley rats were determined by a superfusion technique. It was found that low (1 to 10 nmol/L) concentrations of T3, but not D-T3, rT3, or T4, significantly enhanced Ca-dependent 3H-GABA release by synaptosomes exposed to a high K depolarization buffer for 5 sec. Low concentrations of T3 did not enhance basal 3H-GABA release or release produced by exposure to depolarization buffer for 30 seconds. Much higher concentrations (10 mumol/L) of both T3 and T4, but not rT3, D-T3, or D-T4, stimulated 3H-GABA release produced by exposure to depolarization buffer for 30 seconds.
Hashimoto
H
H
Department of Psychiatry, Kyoto Prefectural University of Medicine, Japan.
Walker
C H
CH
Prange
A J
AJ
Mason
G A
GA
D000818:Animals; D002118:Calcium / Q000502:physiology; D002132:Calcium Radioisotopes; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D009411:Nerve Endings / Q000187:drug effects / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*; D013963:Thyroid Hormones / Q000494:pharmacology*; D013974:Thyroxine / Q000494:pharmacology; D014284:Triiodothyronine / Q000494:pharmacology; D014285:Triiodothyronine, Reverse / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D002132:Calcium Radioisotopes; D013963:Thyroid Hormones; D014284:Triiodothyronine; D005680:gamma-Aminobutyric Acid; D014285:Triiodothyronine, Reverse; D013974:Thyroxine; D011188:Potassium; D002118:Calcium