Title

Role of Muscarinic Acetylcholine Receptors in Pregnant Rat Uterine Cervical Ripening

Department

Biochemistry and Molecular Biology

Publication Year

2009

Abstract

Preterm birth is a frequent scenario in this country and one that often leads to infant mortality. Preterm birth is attributed to premature cervical remodeling. Remodeling of the cervix is a timed event that, in normal pregnancy, allows the fully developed fetus to be expelled from the uterus. Cervical remodeling is characterized by increased cholinergic nerve innervation of the cervix followed by an increase in macrophage trafficking into the cervix by the day before birth. Finally, it is thought that activated macrophages release collagenases and proinflammatory mediators that lead to reduced collagen in the cervix resulting in more pliable tissue. Cholinergic nerves are thought to regulate macrophage trafficking and activation by the released neurotransmitter, acetylcholine. Acetylcholine is able to bind to muscarinic and nicotinic receptors which have been found on macrophages and are present in a remodeling cervix. The main purpose of this study was to terminate the communication between the cholinergic nerves and macrophages within the pregnant rat cervix by introducing an antagonist, atropine, to the muscarinic receptors to inhibit the action of acetylcholine. Atropine is a nonselective muscarinic acetylcholine receptor antagonist. It was immersed into methylcellulose gel; this medicated gel was injected intravaginally into pregnant rats at day 19 of pregnancy. Antagonism of the muscarinic acetylcholine receptor did not affect density of cell nuclei or remodeling of collagen or macrophage census within the cervix when compared to the normal ripening cervix. These findings raise the possibility that the inflammatory-induced ripening of the cervix may be attributed to the action of the nicotinic acetylcholine receptor.

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