In the light of the localization of the peripheral benzodiazepine(pBZD) binding site in hypothalamus, pituitary and adrenal cortex. I have studied the effect of pBZD on the hypothalamo-pituitary axis. In this research, I have used diazepam, clonazepam, and flunitrazepam that have different affinity on pBZD receptor. And this study was undertaken to examine whether the change of plasma ACTH concentration by benzodiazepines(BZD) is midiated GABA-ergic activation.
The plasma ACTH concentration was significantly decreased by diazepam(5mg/kg), clonazepam(5mg/kg) and flunitrazepam(5mg/kg). And those decreases were potenciated by dexamethasone(5mg/kg).
Diazepam-induced decrease of plasma ACTH concentration was moderately inhibited by muscimol(5mg/kg) and it was significantly inhibited by baclofen(5mg/kg) but, not affected by picrotoxin(5mg/kg).
Clonazepam or flunitrazepam-induced decrease of plasma ACTH concentration was significantly inhibited by muscimol , moderately inhibited by baclofen and picrotoxin.
The above results suggest that the decrease of plasma ACTH concentration by BZD is mainly related to pBZD receptor and is influenced by GABA-ergic activation.
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