No Evidence for Activation of 2-Adrenoceptors by Methanolic Extracts of Bovine Brain and Lung Containing Clonidine-Displacing Substance
| Autor: | David A. Kendall, Richard M. Eglen, Darawan Pinthong, V. G. Wilson, S J MacLennan |
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| Rok vydání: | 2003 |
| Předmět: |
Male
Agonist medicine.medical_specialty Swine medicine.drug_class Guinea Pigs Rauwolscine Alpha (ethology) In Vitro Techniques Clonidine General Biochemistry Genetics and Molecular Biology Veins Guinea pig Cyclic nucleotide chemistry.chemical_compound Vas Deferens History and Philosophy of Science Receptors Adrenergic alpha-2 Quinoxalines Internal medicine Cyclic AMP Animals Medicine Rats Wistar Lung Brain Chemistry Tissue Extracts business.industry Methanol General Neuroscience Colforsin Vas deferens Rats Endocrinology medicine.anatomical_structure chemistry Cerebral cortex Brimonidine Tartrate Anesthesia Cattle business Adrenergic alpha-Agonists Idazoxan medicine.drug |
| Zdroj: | Annals of the New York Academy of Sciences. 1009:201-215 |
| ISSN: | 0077-8923 |
| Popis: | Methanolic extracts of bovine brain and lung are capable of displacing [(3)H]-clonidine from alpha(2)-adrenoceptor binding sites, indicating the presence of a clonidine-displacing substance (CDS). We have examined alpha(2)-adrenergic responses and the extracts in three models: [(3)H]-cyclic AMP accumulation in miniprisms of guinea pig cerebral cortex, isometric tension measurements of isolated segments of the rat vas deferens, and porcine palmar lateral vein. The selective alpha(2)-adrenoceptor agonist, 5-bromo-6-2-imidazolin-2-ylamino]-quinoxaline bitartrate (UK-14304) inhibited forskolin-stimulated [(3)H]-cyclic AMP accumulation in the cerebral cortex and elicited contractions of the porcine isolated palmar lateral vein. Clonidine (0.1-30 nM) inhibited neurogenic contractions of the rat vas deferens. Responses to both agonists were inhibited by the alpha(2)-adrenoceptor antagonists, idazoxan or rauwolscine. Brain CDS (5 units/mL) reduced forskolin-stimulated [(3)H]-cyclic AMP accumulation in the guinea pig cerebral cortex, whereas lung CDS (1 unit/mL) increased the accumulation of the cyclic nucleotide. Neither response to the extracts was inhibited by 1 microM idazoxan. Low concentrations of both extracts (0.05 unit/mL) reduced electrically evoked contractions of the rat vas deferens by approximately 20%, but higher concentrations enhanced neurogenic contractions by approximately 50%. Again, the effect of the brain extract was not altered by 1 microM idazoxan. Lung CDS (0.02-1 unit/mL) induced contractions of the porcine palmar lateral vein that were also insensitive to rauwolscine. The results suggest that brain and lung CDS do not activate either central or peripheral alpha(2)-adrenoceptors. |
| Databáze: | OpenAIRE |
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