Effect of thyroid hormones on benzodiazepine receptors in neuron-enriched primary cultures.
The effect of administration of thyroid hormones on central benzodiazepine receptors was investigated using neuron-enriched primary cultures obtained from the neopallium of 16-day-old embryonic rats. Addition of L-triiodothyronine for 3 days decreased the maximal number of benzodiazepine receptor binding sites without any change in affinity at 10(-5) and 10(-6) M. L-Thyroxine administered for 3 days had the same effect at 10(-5) M. No significant change was observed over periods of less than 3 days, a finding indicating that this inhibition was not a direct in vitro effect. This down-regulation seems to be a direct modulatory effect of thyroid hormones on cerebral cortical neurons. Addition for 3 days of D-thyroxine and D-triiodothyronine, which are physiologically inactive isomers of the thyroid hormones, did not induce any significant alterations in benzodiazepine receptors. The decrease in number of cerebral cortical neuronal benzodiazepine receptors due to L-isomers of thyroid hormones may be related to the convulsions and anxiety observed in thyrotoxicosis in humans.
Go
T
T
Department of Pediatrics, Faculty of Medicine, Kyoto University, Japan.
Ito
M
M
Okuno
T
T
Mikawa
H
H
D000818:Animals; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000378:metabolism*; D005445:Flunitrazepam / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011963:Receptors, GABA-A / Q000187:drug effects / Q000378:metabolism*; D013237:Stereoisomerism; D013974:Thyroxine / Q000494:pharmacology*; D014284:Triiodothyronine / Q000494:pharmacology*
D011963:Receptors, GABA-A; D014284:Triiodothyronine; D005445:Flunitrazepam; D013974:Thyroxine