Nitric Oxide May Mediate Nipple Erection

Abstract

The nipple is a specialized structure that can become erect by cold, sexual arousal, breast-feeding, or other tactile stimulations, which can induce the milk ejection reflex and sexual arousal because of intense sensory innervation. The studies that have been conducted thus far to identify the mechanism of nipple erection (NE) are not sufficient. It has been stated that NE occurs via activation of the sympathetic nervous system and smooth muscle contraction. The purposes of this study were to investigate the existence of nitric oxide synthase (NOS) in the nipple-areola complex (NAC) to explain the NE mechanism. Considering that smooth muscle relaxation might be effective in NE, endothelial and neuronal NOS expression and localization were investigated via immunohistochemical methods on sagittal sections from 17 human NACs. The results of this study indicate that eNOS is expressed in the vascular endothelium, ductal epithelium, and smooth muscles, whereas nNOS is expressed in the neural fibers, smooth muscles, ductal epithelium, and vascular endothelium in the NAC. Sinusoidal spaces with endothelial layers similar to those found in penile cavernosal tissue are not found in the NAC. Various mediators are known to affect the function of the NAC smooth muscles; however, this study demonstrates that enzymes (eNOS and nNOS) that synthesize nitric oxide are expressed in the NAC.Key words: Breast physiology, breast-feeding, female sexuality, nitric oxide synthase.J Androl 2012;33:805-810 S tudies concerning sexual function and dysfunction have been predominantly conducted on male sexual health. Smooth muscles and adrenergic innervation are present in the penis, which is the most important erectile organ; however, erection occurs through the relaxation rather than the contraction of these muscles. It is known that nitric oxide (NO) is the most important mediator of erection (Burnett et al, 1992;Rajfer et al, 1992;Lowenstein et al, 1994).Although the number of studies regarding female sexual physiology and pathophysiology have increased in recent years, explanations for female sexual function and dysfunction remain unclear.The female sexual response cycle consists of the desire, arousal (excitement), orgasm, and resolution phases, wherein the primary changes in female sexual organs occur during the arousal phase. Because the primary organs of female sexuality primarily include the vagina and clitoris, most studies have investigated the function and dysfunction of these organs; however, changes in other organs also occur during the arousal phase. The arousal phase of the female sexual response cycle involves genital mechanisms, such as clitoral, labial, and vaginal engorgement, as well as nongenital peripheral mechanisms, such as increases in body secretions, cutaneous vasodilation, increases in breast volume, strained and prominent areola, and nipple erection (NE). Interestingly, the nipple has dual functions in the arousal phase. NE can occur by sexual arousal, and stimulation of the nipple can induce and incre...

RNA-seq analysis for detecting quantitative trait-associated genes

“…Of the validated genes, 10 genes were significantly associated with milk yield in Table 1 . First, NOS3 gene is already reported to be related with milk production, particularly in nipple erection in humans 36 . Because nipple erection is fundamental mechanism for milk production, NOS3 gene would likely be a key marker for milk yield.…”

Characterizing Milk Production Related Genes in Holstein Using RNA-seq

“…ALB is responsible for synthesizing albumin; bovine serum albumin (BSA) is a component of bovine milk ( Pepe et al, 2013 ). NOS3 synthesizes nitric oxide synthase 3; it has been shown to associate with nipple erection in humans ( Tezer et al, 2012 ). Dairy cattle may have an identical mechanism of nipple erection.…”

Correction of Inverted Nipple Using Subcutaneous Turn-Over Flaps to Create a Tent Suspension-Like Effect

“…One of the earliest clinical studies on nipple sensation has revealed erectility of the nipple upon stimulation was found to be most relevant to nipple function, with more objective methods of sensation assessment failing to account for what is physiologically relevant to a patient’s sexual and reproductive needs. [ 21 , 22 ] Hence, we rely on the contractile response upon brush stimulation to most closely represent the ability generate either sexual or suckling response from the nipple. Thus far in our series of patients undergoing the modified method of nipple correction, all of the operated nipples had either retained or recovered the type of sensory perception required for the pilomotor-like response.…”