Ketanserin interaction with urethral alpha-adrenoceptors

Area of Science:

• Pharmacology
• Urology
• Neuroscience

Background:

• Ketanserin is a selective 5-HT2 receptor antagonist.
• Urethral pressure is regulated by various neurotransmitters and receptors.

Purpose of the Study:

• To investigate the effect of ketanserin on urethral pressure in healthy females.
• To explore the in vitro mechanisms of ketanserin's action on the isolated rabbit urethra.

Main Methods:

• Clinical study in healthy females measuring maximal urethral pressures.
• In vitro experiments on isolated female rabbit urethral muscle contractions.
• Assessment of neurotransmitter-induced responses (phenylephrine, noradrenaline, clonidine, 5-HT) and electrical field stimulation.
• Measurement of 3H-noradrenaline efflux.

Main Results:

• Ketanserin reduced maximal urethral pressures by approximately 40% in females without affecting blood pressure.
• In vitro, ketanserin significantly inhibited contractions induced by phenylephrine, noradrenaline, and electrical field stimulation.
• Ketanserin was less effective against clonidine and 5-hydroxytryptamine (5-HT).
• Ketanserin increased 3H-noradrenaline efflux at concentrations above 10(-7) M.

Conclusions:

• Ketanserin counteracts postjunctional alpha 1-adrenoceptor stimulation in the isolated rabbit urethra.
• This mechanism likely explains ketanserin's urethral pressure-lowering effect in humans.