Effect of pregnancy on the cholinergic responses of the bladder: role of acetylcholinesterase

Abstract

Objectives: Pregnancy is associated with many functional changes of the urinary bladder. It was reported that most of healthy women complain from urinary symptoms during pregnancy. The parasympathetic system is mainly mediating bladder emptying. The aim of the study is to investigate the cholinergic effect and the role of acetylcholinesterase in the bladder during pregnancy.

Methods: Sixteen rats were used in the present study as control group (non-pregnant) and pregnant group (18-20 days pregnant). Isolated urinary smooth muscle strips were suspended in organ baths filled with Krebs' solution for isometric tension recording.

Results: Electric field stimulation (EFS), (0.1-40 Hz), of the control and pregnant bladder preparations produced frequency-dependent contractions. Atropine (1 µM) inhibited EFS-induced contractions in the two groups by 65% and 50% respectively indicating the response of cholinergic innervation. Neostigmine significantly enhanced EFS responses, confirming its selectivity for inhibiting acetylcholinesterase which is responsible for termination of acetylcholine. Concentration-response curves for acetylcholine were reduced in pregnant group than control. Concentration-response curves for ATP were increased in pregnant group than control. Neostigmine augmented concentration-response curves for acetylcholine in control and pregnant groups. The effect of neostigmine on acetylcholine contractile responses in pregnancy group was higher than in control.

Conclusions: Urinary bladder dysfunction during pregnancy might be due to augmentation of acetylcholinesterase effect. This will lead to the decrease in response to cholinergic stimuli. New pharmaceutical drugs specifically affecting the enzyme in the bladder can help in avoiding the unpleasant urinary symptoms during pregnancy.

Keywords: Acetylcholinesterase; Bladder; Cholinergic innervation; Muscarinic receptors; Pregnancy.