Volume 15, Number 2 (8-2001)                   Med J Islam Repub Iran 2001 | Back to browse issues page


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MOHAMMADI NAGHADEH M, McGRATH J. POTENTIATION OF RESPONSES TO UK-14304 IN RAT ISOLATED COMMON CAROTID ARTERY BY ANGIOTENSIN. Med J Islam Repub Iran. 2001; 15 (2) :83-88
URL: http://mjiri.iums.ac.ir/article-1-808-en.html

From the Department of Physiology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, I.R. Iran
Abstract:   (2010 Views)
The selective a2 -adrenoceptor agonist UK-14304 produces a small vasoconstrictor response in the rat isolated carotid artery. The purpose of the work presented here was to investigate whether stimuli that produce submaximal contraction would potentiate responses to UK-14304. Male Wistar rats were killed by overdose with pentobarbitone sodium, after which the left and right common carotid arteries were removed. The rings of arteries 3-4 mm in length were cut from each vessel and then mounted in 10 mL isolated organ bath, bathed in Krebs maintained at 37°C and gassed with 95% 02 plus 5% CO2, The preparations were allowed to equilibrate for an hour. Cumulative concentration-response curves (CCRC) were constructed in a cumulative manner by increasing the concentration of the agonists in half-log increments. When antagonists were used, the preparations were incubated at least for 45 minutes with the drugs prior to the onset of a second CCRC. Angiotensin II (All) and other contracting factors were added approximately 10-15 min prior to the onset of CCRC to an agonist. After inducing tone with low concentrations of the thromboxane A2 mimetic agent U-46619 (lnM), 5HT (0.5-1 ).lM) and phenylephrine (l0 nM), exposure of the preparation to UK-14304 resulted in concentration dependent conWrctions to this agonist. The sensitivity and maximum response of the preparation ,to' UK-14304 were not changed. Inducing tone with All (0.01 µM) produc􀁶d a significant leftward shift in the CCRC to UK-14304 (p<0.05). Thus submaximal contraction with All (0.01 µ M) increased responses significantly, but inducing tone with phenylephrine, U-46619 and 5HT had no effect on responses to UK-14304. The α-adrenoceptor antagonists prazosin and rauwolscine were examined to see whether UK-14304's main action in the presence of All remained via al. The potentiated responses were . prazosin sensitive and rauwolscine resistant, indicating an increasing effect mediated by al-adrenoceptors.
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