TY - JOUR T1 - Smooth Muscle Pharmacology in the Isolated Virgin and Pregnant Rat Uterus and Cervix JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther DO - 10.1124/jpet.111.191031 SP - jpet.111.191031 AU - Emma Darios AU - Bridget Seitz AU - Stephanie W Watts Y1 - 2012/01/01 UR - http://jpet.aspetjournals.org/content/early/2012/02/24/jpet.111.191031.abstract N2 - Uterine smooth muscle function is established but comparatively little is known about cervical smooth muscle pharmacology. We performed a proof-of-principle experiment that smooth muscle was expressed in the cervix in both virgin and pregnant rats, using the uterus as a comparator. We tested whether all tissues were pharmacologically responsive to contractile and relaxant agonists. Immunohistochemistry revealed the expression of smooth muscle alpha-actin in all tissues. The isolated tissue bath was used to measure isometric contractility of uterine strips and whole cervices from virgin female Sprague-Dawley rats and pregnant rats (day 11±2). We tested classical activators of uterine smooth muscle contraction and relaxation in both uterus and cervix. All tissues contracted to the depolarizing agent potassium chloride, prostaglandin F2alpha, muscarinic cholinergic agonist carbachol and 5-HT. Unlike other tissues, the pregnant cervix did not contract to oxytocin but the oxytocin receptor was present. Both cervix and uterus (virgin and pregnant) had concentration-dependent, near complete relaxation to the adrenergic agonist norepinephrine and adenylate cyclase activator forskolin. The beta adrenergic receptor agonist isoproterenol was less potent in pregnant cervix vs virgin by ~10 fold. All tissues, particularly the cervix, responded poorly to the nitric oxide donor sodium nitroprusside, relaxing ~20% maximally. These findings support the importance of smooth muscle in the cervix, the use of the isolated cervix in pharmacological studies, and a similarity between smooth muscle pharmacology of the non-pregnant uterus and cervix. This work highlights the unappreciated smooth muscle function of the cervix vs uterus, and cervical changes in pharmacology during pregnancy. ER -