ISSN:
1420-9071
Keywords:
Melatonin
;
hypophysectomy
;
ACTH-derived peptides
;
benzodiazepine receptor
;
brain
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract In this study, we examined the effect of intracerebroventricular (i.c.v) injection of melatonin and/or ACTH1–10 and ACTH4–10 on [3H]flunitrazepam binding sites in the cerebral cortex of hypophysectomized rats. Hypophysectomy increased the Bmax (maximum number of binding sites) of benzodiazepine (BNZ) receptors for at least 7 days after surgery, without changing KD (dissociation constant). The i.c.v. injection of melatonin to hypophysectomized rats significantly increased Bmax, whereas the same doses of melatonin were ineffective in sham-operated animals. In both cases, KD values were unchanged. The i.c.v injection of ACTH1–10 to hypophysectomized animals significantly increased Bmax, an effect that was enhanced by simultaneous i.c.v. injection of ACTH1–10+melatonin, reaching higher values of Bmax than the i.c.v. injection of these hormones individually. No significant changes in KD values were found after ACTH1–10 and/or melatonin administration. However, the i.c.v. injection of ACTH4–10 to hypophysectomized rats did not change Bmax, although it significantly increased KD values, indicating a decrease in the BNZ binding affinity. Melatonin injection counteracted this effect of ACTH4–10, returning KD to the control value. Moreover, although the lower dose of i.c.v. melatonin used, 10 ng, was unable to modify Bmax of BNZ binding in the ACTH4–10-injected group, the higher dose, 20 ng, significantly increased Bmax. The results suggest that these ACTH-derived peptides can modulate the effect of melatonin on brain benzodiazepine receptors.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01931097
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