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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
5
|
| pubmed:dateCreated |
1982-4-12
|
| pubmed:abstractText |
1. The effects of clonidine (1.0 mumol/l) and phentolamine (3.0 mumol/l) on the stimulation-induced efflux of radioactivity were assessed in rat isolated atria and tail arteries in which transmitter stores had been labelled with (3H)-noradrenaline. 2. In atria, clonidine did not affect transmitter release when stimulation was for 10 s periods at frequencies of 1, 2 or 5 Hz, whereas at 10 Hz there was a significant 1.2-fold enhancement of release. Phentolamine enhanced release with stimulation at 5 Hz and 10 Hz by 1.5- and 2.5-fold respectively. 3. In tail arteries, clonidine reduced release when stimulation was for 30 s periods at a frequency of 1 Hz, but did not affect release at 2 Hz or 5 Hz. Phentolamine in each case produced an approximately 1.5-fold enhancement of release. 4. In the pithed rat, spinal stimulation of cardioaccelerator fibres produced a tachycardia, the magnitude of which depended on the frequency and duration of stimulation. Clonidine (10 micrograms/kg, i.v.) caused either a reduction or an enhancement of the response depending on the frequency and duration of stimulation; in the presence of phentolamine (2 mg/kg, i.v.), clonidine had no effect. 5. The results are consistent with partial agonistic actions of clonidine at prejunctional alpha-adrenoceptors in the rat cardiovascular system; such effects may be of relevance to the mechanism of the clonidine withdrawal syndrome.
|
| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
IM
|
| pubmed:chemical | |
| pubmed:status |
MEDLINE
|
| pubmed:issn |
0305-1870
|
| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:volume |
8
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
503-7
|
| pubmed:dateRevised |
2006-11-15
|
| pubmed:meshHeading |
pubmed-meshheading:6276062-Animals,
pubmed-meshheading:6276062-Arteries,
pubmed-meshheading:6276062-Clonidine,
pubmed-meshheading:6276062-Electric Stimulation,
pubmed-meshheading:6276062-Female,
pubmed-meshheading:6276062-Heart,
pubmed-meshheading:6276062-Heart Atria,
pubmed-meshheading:6276062-Humans,
pubmed-meshheading:6276062-Intercellular Junctions,
pubmed-meshheading:6276062-Male,
pubmed-meshheading:6276062-Rats,
pubmed-meshheading:6276062-Rats, Inbred Strains,
pubmed-meshheading:6276062-Receptors, Adrenergic,
pubmed-meshheading:6276062-Receptors, Adrenergic, alpha,
pubmed-meshheading:6276062-Sympathetic Nervous System,
pubmed-meshheading:6276062-Synaptic Transmission,
pubmed-meshheading:6276062-Tachycardia,
pubmed-meshheading:6276062-Tail
|
| pubmed:articleTitle |
Dual effects of clonidine on rat prejunctional alpha-adrenoceptors.
|
| pubmed:publicationType |
Journal Article,
Research Support, Non-U.S. Gov't
|