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1 Department of Physiology and 2 Department of Internal Medicine, Miyazaki Medical College, Miyazaki 889-1692, Japan
Adrenomedullin (ADM) is
reported to be a peripherally acting hypotensive peptide, but its
central actions are unclear. We investigated the effects of centrally
administered ADM on blood pressure (BP), heart rate (HR), and renal
sympathetic nerve activity (RSNA) in conscious rats and
sinoaortic-denervated (SAD) rats. We also investigated the receptors
interacting with ADM using two putative antagonists.
Intracerebroventricular administration of ADM in doses of 0.1 and 0.5 nmol/kg caused tachycardia and early inhibition of RSNA. Central ADM
(1.0 nmol/kg) induced hypertension, tachycardia, and a decrease
followed by an increase in RSNA. In SAD rats, increases in BP, HR, and
RSNA at the late phase were enhanced by central ADM (1.0 nmol/kg),
whereas the early decrease in RSNA remained. Thus the inhibition of
RSNA via central ADM may be unrelated to the arterial baroreceptor
reflex. Pretreatment with antagonists human calcitonin gene-related
peptide-(8
37) and human ADM-(22
52) significantly suppressed the
central actions of ADM. The findings suggest that ADM is involved as a
neuropeptide in the receptor-mediated central regulation of the
cardiovascular system and RSNA.
renal sympathetic nerve activity; sinoaortic-denervated rats; receptor antagonists; neuropeptide
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