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| Content Provider | World Health Organization (WHO)-Global Index Medicus |
|---|---|
| Author | Kirkpatrick, K. A. Burnstock, G. Mackenzie, I. |
| Description | Author Affiliation: MacKenzie I ( Department of Anatomy and Developmental Biology, University College, London.) |
| Abstract | 1. The agonistic and antagonistic effects of two nucleotide analogues, P1,P5-di-(adenosine-5') pentaphosphate (AP5A) and alpha,beta-methylene ATP (alpha,beta-Me ATP), have been compared in the guinea-pig isolated vas deferens. 2. In organ bath studies, both AP5A and alpha,beta-Me ATP were approximately 100 times more potent than ATP in producing phasic contractions of the vas deferens smooth muscle. Repeated additions of either agonist (1-10 microM) produced desensitization to a subsequent addition of the test substance. AP5A and alpha,beta-Me ATP were approximately equipotent in the production of desensitization. 3. After desensitization had been produced in the vas deferens by AP5A or alpha,beta-Me ATP, excitatory responses elicited by ATP (100-150 microM) and nonadrenergic field stimulation (2-20 Hz) were blocked, whereas those elicited by carbachol (1-10 microM) were augmented. 4. Intracellular electrical recordings demonstrated that AP5A and alpha,beta-Me ATP produced similar effects on membrane activity of the vas deferens. Concentration-dependent depolarizations alone were produced by both substances until the voltage threshold for action potential discharge was attained; thereafter, action potential discharges were superimposed on the depolarization and an accompanying phasic contraction was recorded. Upon restoration of the membrane potential to its control value (5-10 min after addition of either AP5A or alpha,beta-Me ATP), excitatory junction potentials (e.j.ps) elicited by field stimulation (up to 3 Hz) and spontaneous e.j.ps were reduced by AP5A (greater than 0.1 microM) in a concentration-dependent manner (as previously described for alpha,beta-Me ATP). 5. The antagonistic effects of APA on mechanical responses elicited by field stimulation were more quickly reversed on washout of AP5A than were the effects of X,f-Me ATP, suggesting some dissimilarity in their mechanism of action at the receptor level. 6. The antagonistic effects of AP5A on the nonadrenergic contractile responses of the vas deferens were not produced by the structurally related P',P4-di-(adenosine-5') tetraphosphate (AP4A) even with cumulative concentrations up to 200 pM. 7. Desensitization of P2-purinoceptors can be produced by some nucleotide analogues such as AP5A and a,fi-Me ATP, whose activity may arise partly because of their structural conformation and stability. |
| ISSN | 00071188 |
| e-ISSN | 14765381 |
| Journal | British Journal of Pharmacology |
| Issue Number | 3 |
| Volume Number | 94 |
| Language | English |
| Publisher | Wiley Online Library(on behalf of The British Pharmacological Society) |
| Publisher Date | 1988-07-01 |
| Publisher Place | Great Britain (UK) |
| Access Restriction | Open |
| Subject Keyword | Adenosine Triphosphate Analogs & Derivatives Dinucleoside Phosphates Pharmacology Muscle, Smooth Drug Effects Action Potentials Animals Guinea Pigs In Vitro Techniques Muscle Contraction Vas Deferens Comparative Study Research Support, Non-U.S. Gov't |
| Content Type | Text |
| Resource Type | Article |
| Subject | Pharmacology |
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