The roles of α₂-adrenoceptor subtypes in the control of cervical resistance in the late-pregnant rat

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• 作者：Adrienn Gá ; l ; Eszter Ducza ; Rená ; ta Minorics ; Anna Klukovits ; Má ; rta Gá ; lik ; George Falkay ; Ró ; bert Gá ; spá ; r
• 关键词：α ; ₂-adrenoceptor ; Subtype-selective antagonist ; Pregnancy ; Cervical resistance ; Cyclic AMP ; (Rat)
• 刊名：European Journal of Pharmacology
• 出版年：2009
• 出版时间：1 August 2009
• 年：2009
• 卷：615
• 期：1-3
• 页码：193-200
• 全文大小：918 K

文摘

The roles of the α₂-adrenoceptor subtypes in the regulation of cervical resistance have previously not been investigated. The aim of the present study was to identify these receptors in the late-pregnant cervix and determine their functions in vitro in the rat. The expressions of the α₂-adrenoceptor subtypes were determined by means of RT-PCR and Western blotting techniques. The changes in cervical resistance due to subtype-selective antagonists were investigated in stretching tests. The cyclic AMP immunoassay technique was used to detect the level of cyclic AMP following stimulation of the α₂-adrenoceptors with or without pertussis toxin. On pregnancy days 18, 20, 21 and 22, the RT-PCR and Western blotting studies revealed the expressions of all three α₂-adrenoceptor subtype mRNAs and proteins. On days 18 and 20, noradrenaline increased and decreased the resistance, respectively. Its effect was blocked by each of the antagonists used, except ARC 239 on both days. On day 21, noradrenaline again increased the resistance, this effect being maintained only in the presence of spiroxatrine. Noradrenaline was ineffective on day 22. These results were supported by the changes in cyclic AMP levels. Pertussis toxin pretreatment eliminated the changes in the cyclic AMP level on days 18 and 21. We presume that the α_2A- and α_2C-adrenoceptors play predominant roles in the regulation of cervical resistance on days 18–21. Depending on the day of pregnancy, stimulation of these α₂-adrenoceptors could even result in opposite effects. This fluctuation can be explained by the changes in the G_i/G_s-coupling of the α_2A- and α_2C-adrenoceptors.