Abstract
In accord with previous studies intracerebroventricular (i.c.v.) injections of ACTH1-24 (1 μg) induced a display of excessive grooming, and increased the plasma concentrations of ACTH and corticosterone. Pituitary-adrenal activation was blocked by pretreatment with dexamethasone, indicating that the effect of the (i.c.v.) injected peptide was not caused by a peripheral effect on the adrenal cortex.
Doses of 1 and 3 μg of a non-selective melanocortin-3/4-receptor antagonist (SHU 9119), or of 5 and 10 μg of a selective melanocortin-4-receptor antagonist ([D-Arg8]ACTH4-10), coadministered (i.c.v.) with 1 μg ACTH1-24, inhibited the ACTH1-24-induced activation of the hypothalamus-pituitary-adrenal-axis and excessive grooming.
In addition, several doses of the selective melanocortin-3-receptor agonist Lys-γ2-MSH were centrally administered, but neither neuroendocrine, nor excessive grooming responses were observed.
These results imply that the melanocortin-4-receptor, and not the melanocortin-3-receptor, is involved in the ACTH1-24-induced rise in plasma levels of ACTH and corticosterone, and excessive grooming.
Keywords: Melanocortin-4-receptor, melanocortin-3-receptor, melanocortin receptor antagonist, ACTH, corticosterone, grooming
Full Text
The Full Text of this article is available as a PDF (311.3 KB).