Korean J Urol.  2011 Feb;52(2):136-141.

Leptin Enhances Nitric Oxide-Dependent Relaxation of the Clitoral Corpus Cavernosum

• Lee SY
• Chung WH
• Lee MY
• Kim SC
• Kim HW
• Myung SC

Abstract

PURPOSE
The effects of leptin on female sexual behaviors are controversial, and studies on this topic are limited. The objectives of this study were to evaluate the direct effects of leptin on clitoral vasoreactivity in vitro and to determine the mechanism of action.
MATERIALS AND METHODS
Isometric tension studies were conducted to determine the effects of pretreatment with leptin (10(-8) M) on the contractile responses of rabbit clitoral corpus cavernosal smooth muscle strips. The effects of leptin were assessed on precontraction induced by phenylephrine (PE; 10(-9)-10(-4) M) and KCl (35-140 mM). We also examined the effect of leptin on relaxation induced by acetylcholine (ACh; 10(-9)-10(-4) M), verapamil (10(-10)-10(-6) M), and sodium nitroprusside (10(-9)-10(-4) M) in PE-precontracted (10(-5) M) strips.
RESULTS
Leptin enhanced ACh-induced relaxation in PE-precontracted strips. L-NAME pretreatment significantly reduced the effect of leptin on ACh-induced relaxation, whereas L-arginine potentiated the effect of leptin. Leptin decreased the KCl-induced contractile responses. Leptin increased verapamil-induced relaxation responses. The relaxation effects of leptin on KCl-induced contraction were inhibited by 10(-5) M methylene blue and L-NAME pretreatment.
CONCLUSIONS
A high concentration of leptin enhances ACh-dependent relaxation in clitoral cavernosal smooth muscles. These relaxation effects of leptin may occur through an NO-dependent mechanism and voltage-dependent calcium channel blockade.

Keyword

Calcium channels; Clitoris; Leptin; Nitric oxide; Relaxation

MeSH Terms

Acetylcholine
Arginine
Calcium Channels
Clitoris
Contracts
Female
Humans
Leptin
Methylene Blue
Muscle, Smooth
NG-Nitroarginine Methyl Ester
Nitric Oxide
Nitroprusside
Phenylephrine
Relaxation
Sexual Behavior
Verapamil
Acetylcholine
Arginine
Calcium Channels
Leptin
Methylene Blue
NG-Nitroarginine Methyl Ester
Nitric Oxide
Nitroprusside
Phenylephrine
Verapamil

Figure

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  FIG. 1 Concentration-response curves for the effect of leptin pretreatment on contraction in rabbit clitoral corpus cavernosal strips in a phenylephrine dose-dependent manner (n=8).

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  FIG. 2 Concentration-response curves for the effect of leptin pretreatment on relaxation in rabbit clitoral corpus cavernosal strips in an acetylcholine dose-dependent manner. The preparation was preconstricted with 10-5 M PE. n=12; a: p<0.05.

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  FIG. 3 Concentration-response curves for the effect of leptin pretreatment of rabbit clitoral corpus cavernosal strips in high-concentration K solution. n=8; a: p<0.05.

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  FIG. 4 Concentration-response curves for the effect of leptin pretreatment on verapamil responses in rabbit clitoral corpus cavernosal strips. The preparation was preconstricted with 10-5 M PE. n=12; a: p<0.05.

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  FIG. 5 Concentration-response curves for the effect of leptin pretreatment on ACh responses in cavernosal strips treated with 10-5 M L-NAME (A) or 0.1 mM L-arginine (B). The preparation was preconstricted with 10-5 M PE. n=12 in each. a: p<0.05 compared with control, b: p<0.01 compared with control.

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  FIG. 6 Concentration-response curves for the effects of pretreatment with L-NAME (A) or methylene blue (B) on rabbit clitoral corpus cavernosal strips with increasing leptin doses. The preparation was preconstricted with 70 mM KCl solution. n=8 in each; a: p<0.05.

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