Document Detail


Mechanisms of the regional hemodynamic effects of a mu-opioid receptor agonist microinjected into the hypothalamic paraventricular nuclei of conscious unrestrained rats.
MedLine Citation:
PMID:  8996229     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The present study was undertaken to characterize the mechanisms of the hemodynamic responses to microinjection of the selective mu-opioid receptor agonist [D-Ala2,MePhe4,Gly5-ol]enkephalin (DAMGO) into the paraventricular nucleus of the hypothalamus, in conscious rats chronically instrumented with pulsed Doppler flow probes. We found that i.v. pretreatment with phentolamine had no effect on the tachycardia elicited by DAMGO (1 nmol); however, the pressor response was reversed to a state of hypotension, the renal and superior mesenteric vasoconstrictions were attenuated and the hindquarter vasodilation was potentiated. In the presence of propranolol, the pressor response and renal vasoconstriction were unchanged, whereas the superior mesenteric vasoconstriction was reduced and the hindquarter vasodilation was abolished. Moreover, in those animals we observed bradycardia followed by tachycardia. Combined i.v. pretreatment with phentolamine and propranolol abolished the pressor and heart rate responses to DAMGO but had no effect on the renal and superior mesenteric vasoconstrictions, although the hindquarter vasodilation was reduced. Intravenous pretreatment with a vasopressin V1 receptor antagonist or captopril had no effect on the cardiovascular responses to DAMGO. Together, these results indicate that the hypertension observed after injection of DAMGO into the paraventricular nucleus of the hypothalamus was secondary to alpha adrenoceptor-mediated vasoconstrictions in renal and superior mesenteric vascular beds and to beta adrenoceptor-mediated vasodilation in the hindquarter vascular bed, whereas the involvement of circulating vasopressin or angiotensin seems less obvious from the present findings. However, we cannot exclude the possibility that nonadrenergic, nonvasopressinergic and nonangiotensinergic vasoconstrictor mechanisms were acting in the renal and superior mesenteric vascular beds.
Authors:
H Bachelard; M Pître; A Lessard
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of pharmacology and experimental therapeutics     Volume:  280     ISSN:  0022-3565     ISO Abbreviation:  J. Pharmacol. Exp. Ther.     Publication Date:  1997 Jan 
Date Detail:
Created Date:  1997-02-10     Completed Date:  1997-02-10     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0376362     Medline TA:  J Pharmacol Exp Ther     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  460-70     Citation Subset:  IM    
Affiliation:
Unité de Recherche sur l'Hypertension, Centre de Recherche du CHUL, Université Laval, Ste-Foy, Canada.
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MeSH Terms
Descriptor/Qualifier:
Animals
Captopril / pharmacology
Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
Enkephalins / administration & dosage,  pharmacology*
Hemodynamics / drug effects*
Male
Microinjections
Paraventricular Hypothalamic Nucleus / drug effects*
Phentolamine / pharmacology
Propranolol / pharmacology
Rats
Rats, Inbred WKY
Receptors, Opioid, mu / agonists*
Receptors, Vasopressin / antagonists & inhibitors
Chemical
Reg. No./Substance:
0/Enkephalins; 0/Receptors, Opioid, mu; 0/Receptors, Vasopressin; 100929-53-1/Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; 50-60-2/Phentolamine; 525-66-6/Propranolol; 62571-86-2/Captopril

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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