Characterization of bulbospongiosus muscle reflexes activated by urethral distension in male rats

Sucrose consumption modifies the urethrogenital reflex and histological organization of the bulbospongiosus muscle in the male rat

Disorders of the bulbospongiosus muscle (Bsm) are associated with male sexual dysfunction, such as premature ejaculation. We determined the effect of sucrose-water consumption during pregnancy-lactation and postnatal on reflex responses and morphology of Bsm fibers in adult male Wistar rat offspring. Female rats were mated and grouped into consumed tap water mothers and sucrose-water (5 %) mothers during pregnancy-lactation to obtain experimental groups. Male pups were weaned and assigned into four groups (n = 12; each group). Those from control mothers who continued drinking tap water (CM-CO group) or sucrose water (CM-SO group), and those from sucrose mothers who drank tap water (SM-CO group) or continued drinking sucrose water (SM-SO group) until adult life. In male rat offspring (n = 6 per group) was recorded the electrical activity of Bsm was recorded during penile stimulation and urethrogenital reflex (UGR). Other male rat offspring were designated for histological analysis (n = 6 per group). Sucrose consumption during prenatal stages increased the frequency of the Bsm during UGR, while pre and postnatal consumption modified muscle fiber cross-sectional area and increased the collagen content, suggesting that a combination of a diet with pre- and postnatal sucrose changes the Bsm morphophysiology possibly causing male sexual dysfunctions.

Developing a Novel Method for the Analysis of Spinal Cord-Penile Neurotransmission Mechanisms

Sexual dysfunction can be caused by impaired neurotransmission from the peripheral to the central nervous system. Therefore, it is important to evaluate the input of sensory information from the peripheral genital area and investigate the control mechanisms in the spinal cord to clarify the pathological basis of sensory abnormalities in the genital area. However, an in vivo evaluation system for the spinal cord-penile neurotransmission mechanism has not yet been developed. Here, urethane-anesthetized rats were used to evaluate neuronal firing induced by innocuous or nociceptive stimulation of the penis using extracellular recording or patch-clamp techniques in the lumbosacral spinal dorsal horn and electrophysiological evaluation in the peripheral pelvic nerves. As a result, innocuous and nociceptive stimuli-evoked neuronal firing was successfully recorded in the deep and superficial spinal dorsal horns, respectively. The innocuous stimuli-evoked nerve firing was also recorded in the pelvic nerve. These firings were suppressed by lidocaine. To the best of our knowledge, this is the first report of a successful quantitative evaluation of penile stimuli-evoked neuronal firing. This method is not only useful for analyzing the pathological basis of spinal cord-penile neurotransmission in sexual dysfunction but also provides a useful evaluation system in the search for new treatments.

Secondary urethral sphincter function of the rabbit pelvic and perineal muscles

Perineal and pelvic floor muscles play an important role in continence by providing mechanical support to pelvic organs. It is also known that the pubococcygeus muscle (PcM) contracts in the storage phase and is inactive during voiding, while the bulbospongiosus muscle (BsM) is active during the voiding phase. Recent evidence suggested an additional role of these muscles in supporting urethral closure in rabbits. However, the individual role of perineal and pelvic muscles as urethral sphincters is not well-defined. Here we evaluated the individual, sequential and synergistic roles of the PcM and BsM in assisting urethral closure and defined the optimal electrical stimulation parameters that can effectively contract these muscles and increase the urethral pressure (P _ura ) in young nulliparous animals (n = 11). Unilateral stimulation of either the BsM or PcM at 40 Hz induced modest increases in average P _ura (0.23 ± 0.10 and 0.07 ± 0.04 mmHg, respectively). Investigation on the changes in P _ura evoked by stimulation frequencies between 5 and 60 Hz show that sequential contralateral PcM-BsM activation at 40 Hz induced a 2-fold average P _ura increase (0.23 ± 0.07 mmHg) compared to that evoked by PcM stimulation. Simultaneous activation of PcM and BsM at 40 Hz also showed an increased average P _ura (0.26 ± 0.04 mmHg), with a 2-fold increase in average P _ura observed during the unilateral sequential PcM-BsM stimulation at 40 Hz (0.69 ± 0.2 mmHg). Finally, stimulation at 40 Hz of the bulbospongiosus nerve (BsN) induced an approximate 4-fold increase in average P _ura (0.87 ± 0.44 mmHg; p < 0.04) compared to that elicited by BsM stimulation, confirming that direct nerve stimulation is more effective. Together, this study shows that in the female rabbit, both perineal and pelvic muscles support of the urethral function during continence, and that unilateral stimulation of the BsN at 40-60 Hz is sufficient to achieve maximal secondary sphincter activity. The results also support the potential clinical value of neuromodulation of pelvic and perineal nerves as bioelectronic therapy for stress urinary incontinence.

Post Orgasmic Illness Syndrome (POIS) and Delayed Onset Muscle Soreness (DOMS): Do They Have Anything in Common?

Post orgasmic illness syndrome is a rare, mysterious condition with an unknown pathomechanism and uncertain treatment. The symptoms of post orgasmic illness syndrome last about 2–7 days after an ejaculation. The current hypothesis proposes that the primary injury in post orgasmic illness syndrome is an acute compression proprioceptive axonopathy in the muscle spindle, as is suspected in delayed onset muscle soreness. The terminal arbor degeneration-like lesion of delayed onset muscle soreness is theorized to be an acute stress response energy-depleted dysfunctional mitochondria-induced impairment of Piezo2 channels and glutamate vesicular release. The recurring symptoms of post orgasmic illness syndrome after each ejaculation are suggested to be analogous to the repeated bout effect of delayed onset muscle soreness. However, there are differences in the pathomechanism, mostly attributed to the extent of secondary tissue damage and to the extent of spermidine depletion. The spermidine depletion-induced differences are as follows: modulation of the acute stress response, flu-like symptoms, opioid-like withdrawal and enhanced deregulation of the autonomic nervous system. The longitudinal dimension of delayed onset muscle soreness, in the form of post orgasmic illness syndrome and the repeated bout effect, have cognitive and memory consequences, since the primary injury is learning and memory-related.

Sucrose exposure during gestation lactation and postweaning periods increases the pubococcygeus muscle reflex activity in adult male rats

Erectile dysfunction is related to metabolic alterations produced by a high carbohydrate diet, which may affect muscle activity during penile reflex in adulthood. We determined whether sucrose water consumption during gestation lactation and postweaning affects pubococcygeus muscle (Pcm) activity during urethrogenital reflex in adult male rat offspring. Twelve female rats were mated and grouped in control mothers consumed tap water and sucrose mothers consumed sucrose water during gestation lactation. Male pups were weaned and assigned into four groups (n = 6 each): those from control mothers who continued drinking tap water (CM-CO group) or sucrose water (CM-SO group) until adult life, and those from sucrose mothers who drank tap water (SM-CO group) or continued drinking sucrose water (SM-SO group) until adult life. Body weight, Pcm activity during penile stimulation by bipolar electrodes and urethrogenital reflex were analyzed. A catheter was placed into the urethra to record variations in urethral pressure after mechanical stimulation. Two-way ANOVA followed by post hoc tests were used considering P ≤ 0.05 as a significant difference. Males from the SM-SO group showed weight gain compared to the control group (P < 0.001). Also, sucrose intake promoted high Pcm activity (P < 0.0001) but reduced urethrogenital reflex duration CM-CO vs CM-SO (P = 0.02); CM-CO vs SM-CO (P = 0.01); CM-SO vs SM-SO (P < 0.003); and SM-CO vs SM-SO (P < 0.002). Our results suggest that a combination of a sucrose-rich diet during gestation lactation and postweaning modifies Pcm activation during penile reflex. The urethrogenital reflex is a spinal ejaculatory-like reflex, these rats could have penile dysfunction equivalent to premature ejaculation in men.

[Urethral reflexes: A review]

INTRODUCTION

The urethrosphincter complex is involved not only in maintaining urinary continence, particularly during effort, but also for the achievement of a complete and effective micturition. Indeed, the urethra is not a simple passive channel for the evacuation of urine from the bladder to the urethral meatus, since its resistive capacities and its possibilities of modulation of the micturition reflex depend on its reflex role either as a sensory afferent or as a neuro-muscular effector. It also participates in many genito-sexual and ano-rectal réflexes.

MATERIAL AND METHOD

This review of the literature describes the various reflexes of the urethra as a sensory stimulus or a neuromuscular effector. All articles referenced in this review were obtained from articles indexed on Pubmed-Medline, using the keywords: "urethral reflexes; "reflex bladder"; "urination reflex"; "intravaginal; vaginal"; "anorectal; sphincter"; "Storage and voiding"; "reflexes sneezing"; "cough reflex". Other articles were selected through references of the articles issued from the first research. Only articles in English and French have been selected. The articles concerned animal and human experiments.

RESULTS

Eight hundred and sixty-four referenced articles were founded and a total of 75 articles were included, describing the various reflexes mediated by the urethra acting as a sensory afferent or mechanical effector. We differentiated the known data in humans and animals.

CONCLUSION

The urethra is a complex anatomical structure ensuring, through numerous reflex mechanisms, urinary continence. Urethral resistances are modulated during efforts and depends on the bladder capacity and the intensity of the efforts. During micturition, the coordination between the bladder and the urethra is mediated by reflex pathways organized at the cerebral, spinal and lumbosacral levels. The modulation of the micturition in term of efficacy and velocity, is due in part, to the re-afferentation of the spinal reflex by continuous stimulus of the urethral canal. Many of these reflexes are imperfectly described. Finally, the urethra is implicated in reflex loops of anal continence and sexual functions.

Association of NE, leptin, and 5-HT with electrophysiological parameters in patients with primary premature ejaculation

OBJECTIVE

To investigate the possible role of serum norepinephrine (NE), leptin, and 5-hydroxytryptamine (5-HT) and their correlations with sympathetic skin response located in the penis (PSSR) in primary premature ejaculation (PPE).

METHODS

We compared the serum level of NE, leptin, and 5-HT, intravaginal ejaculatory latency time (IELT) and the premature ejaculation diagnostic tool (PEDT) scores between 57 PPE patients and 42 healthy control men as controls, who were recruited between September 2016 and January 2019. Additionally, the amplitude and latency of PSSR were measured and compared between the two groups.

RESULTS

Compared with healthy men, both leptin and NE increased significantly in PPE patients (P = .003, P = .005), while serum 5-HT remarkably decreased (P = .002). Serum leptin, NE, and 5-HT were significantly correlated with the diagnosis of PPE, PSSR amplitude, and latency. Moreover, compared with single serum indicator, NE/5-HT and leptin/5-HT had a stronger correlation with both PSSR amplitude (r = .8377, P < .001; r = .9323, P < .001, respectively) and latency (r = -.8058, P < .001; r = -.8901, P < .001, respectively).

CONCLUSION

Significant differences in leptin, NE, and 5-HT are observed between PPE patients and the controls, which supports the hypothesis of hyperactive sympathetic nerve system (SNS) in PPE. Additionally, leptin/5-HT ratio may serve as an ideal indicator for reflecting SNS activity and predicting treatment response in PPE patients in the future.

Chronic, Twice-Daily Dosing of an NK2 Receptor Agonist [Lys5,MeLeu9,Nle10]-NKA(4-10), Produces Consistent Drug-Induced Micturition and Defecation in Chronic Spinal Rats

Acute administration of [Lys5,Me,Leu9,Nle10]-NKA(4-10) (LMN-NKA) produces contractions of the detrusor and rectum with voiding in intact and acutely spinal cord injured (SCI) rats. In the current study, the ability of LMN-NKA (10 μg/kg or 100 μg/kg, subcutaneous [SC], twice a day [bid]) or vehicle to induce voiding and defecation in chronic SCI rats was examined across 30 days. After the last day of administration, voiding response rates and bladder pressure (BP) responses to LMN-NKA (intravenous [IV] and SC) were evaluated under anesthesia. In conscious rats, LMN-NKA (100 μg/kg) produced dose-dependent micturition within 5 min, with response rates >90%, and voiding efficiency >80% in males and >60% in females, which remained stable across the 1-month test period. Similarly, LMN-NKA administration rapidly induced defecation, which also remained stable. Under anesthesia, LMN-NKA increased BP, voiding efficiency, and voiding response rates, which reached 100% at 3 and 10 μg/kg IV in males and females, respectively. SC administration produced 100% response rates in males (30 μg/kg) but only 71% in females (100 μg/kg). Efficacy in rats chronically treated with LMN-NKA was similar to naïve and vehicle-treated rats, except for reduced voiding efficiency in chronically dosed female rats (100 μg/kg). No differences in bladder weights or collagen-to-smooth muscle ratios in histological sections were seen between the groups. Thus neither tolerance, nor sensitization, to LMN-NKA-induced micturition and defecation occurs with chronic administration in rats with chronic SCI. Efficacy was higher in male than in female rats.

Somatic innervation contributes to the release of bulbourethral gland secretion in male rats

BACKGROUND

In male rats, the bulbourethral glands (Bu-Gs) are the unique accessory sexual glands surrounded by striated musculature. However, until now the role of this musculature was unknown.

OBJECTIVES

(i) To characterize the Bu-Gs striated muscular layer in male rats and determine its innervation and response to genital stimulation. (ii) To reveal the role of the Bu-Gs striated musculature in the release of glandular secretion. (iii) To elucidate the effect of bilateral ablation of the Bu-Gs on copulatory behavior and seminal fluid characteristics.

MATERIALS AND METHODS

Adult Wistar male rats were allocated in three experiments: in Experiment 1, the Bu-Gs striated musculature, innervation and reflex activity were determined by gross anatomy and histological and electrophysiological techniques; electromyographic activity of the Bu-Gs striated musculature was evoked with genital stimulation. In Experiment 2, Bu-Gs were analyzed after copulatory behavior of intact or animals with unilateral transected motor branch of the sacral plexus (MBSP). In Experiment 3, copulatory behavior and spermatobioscopy of males with bilateral ablation of the Bu-Gs or sham surgery were analyzed.

RESULTS

The Bu-Gs striated fibers discharged in response to mechanostimulation of the prepuce, glans, and penile-urethra. Innervation of the Bu-Gs striated musculature originated from the MBSP; this nerve also innervates striated penile muscles. Unilateral transection of the MBSP significantly decreased the secretion from the ipsilateral Bu-G to the nerve transection. Bilateral ablation of Bu-Gs did not affect seminal plug formation but decreased semen viscosity.

DISCUSSION AND CONCLUSION

The Bu-Gs striated musculature contributes to expel glandular secretion during sexual intercourse. The somatic control of Bu-Gs secretion is additional to the reported autonomic innervation supplied by the cavernosus nerve, which may underlie the synthesis of secretion as well as contraction of Bu-Gs smooth muscle.

Characterization and in vivo efficacy of a heptapeptide ODT formulation for the treatment of neurogenic bladder dysfunction

The objective of this study was to develop oral disintegrating tablet (ODT) formulations of a heptapeptide, [Lys5,MeLeu9,Nle10]-NKA(4-10), for the treatment of neurogenic bladder dysfunction. A design of experiment approach was applied to determine the optimal ratio of chosen excipients: gelatin (X1), glycine (X2), and sorbitol (X3). These formulations were optimized for efficacy studies to produce ODTs exhibiting rapid disintegration times (Y1) and appropriate structural integrity (Y2) using JMP® 12.0.1 software. Based on theoretically predicted values from 12 experimental runs, the optimal ODT formulation was determined to be 3% (w/v) gelatin, 2% (w/v) glycine, and 1% (w/v) sorbitol in deionized water. Using this formulation, blank and drug-loaded ODTs containing 1.5 mg or 5 mg of [Lys5,MeLeu9,Nle10]-NKA(4-10) were manufactured by a lyophilization process. The peptide-loaded tablets disintegrated in less than 30 s and released 97% of the peptide within 15 min. The peptide was stable for 90 days under 25 °C/60% relative humidity (RH) and 40 °C/75% RH. In vivo efficacy of the peptide-loaded ODTs was confirmed in a rat acute spinal cord injury model under isovolumetric bladder pressure recording conditions, concluding that sublingual administration of peptide-containing ODTs evoke a rapid dose-related neurokinin 2-mediated increase in bladder pressure.

Pharmacodynamic evaluation of Lys5, MeLeu9, Nle10-NKA(4-10) prokinetic effects on bladder and colon activity in acute spinal cord transected and spinally intact rats

The purpose of this study was to determine feasibility of a novel therapeutic approach to drug-induced voiding after spinal cord injury (SCI) using a well-characterized, peptide, neurokinin 2 receptor (NK2 receptor) agonist, Lys5, MeLeu9, Nle10-NKA(4-10) (LMN-NKA). Cystometry and colorectal pressure measurements were performed in urethane-anesthetized, intact, and acutely spinalized female rats. Bladder pressure and voiding were monitored in response to intravenous LMN-NKA given with the bladder filled to 70% capacity. LMN-NKA (0.1-300 μg/kg) produced dose-dependent, rapid (<60 s), short-duration (<15 min) increases in bladder pressure. In intact rats, doses above 0.3-1 μg/kg induced urine release (voiding efficiency of ~70% at ≥1 μg/kg). In spinalized rats, urine release required higher doses (≥10 μg/kg) and was less efficient (30-50%). LMN-NKA (0.1-100 μg/kg) also produced dose-dependent increases in colorectal pressure. No tachyphylaxis was observed, and the responses were blocked by an NK2 receptor antagonist (GR159897, 1 mg/kg i.v.). No obvious cardiorespiratory effects were noted. These results suggest that rapid-onset, short-duration, drug-induced voiding is possible in acute spinal and intact rats with intravenous administration of an NK2 receptor agonist. Future challenges remain in regard to finding alternative routes of administration that produce clinically significant voiding, multiple times per day, in animal models of chronic SCI.

The role of the pubococcygeus muscle in the urethrogenital reflex of male rats

AIM

To determine the response of the pubococcygeus muscle (Pcm) during the urethrogenital reflex (UGR).

METHODS

Urethane-anesthetized male rats (n = 20) were used to describe the gross anatomy of the Pcm (n = 3), the effect of the electrical stimulation of the Pcm on the urethral pressure (n = 3), and the reflex activity of the Pcm due to the mechanical stimulation of the urethra (n = 3) and during penile and urethrogenital reflexes (n = 11). The urethral pressure (UP) was recorded as a response to penile stimulation (brushing, extension, and occlusion) and during the UGR; the electromyographic activity of the Pcm was simultaneously evaluated. The role of the Pcm was assessed by measuring urethral pressure variables before and after denervation of this muscle.

RESULTS

The Pcm is innervated by the caudal branch of the somatomotor branch of the pelvic nerve. The electrically induced contraction of the Pcm increased the UP. The mechanical stimulation of the urethra during the induced micturition caused the reflex activity of the Pcm. The different penile stimuli caused bursts of activity of the Pcm. During the UGR, the Pcm exhibited a tonic activity. The transection of the caudal branch of the Smb reduced the maximal UP during the penile stimulation. The same was true regarding the duration of the UGR, the pressure that triggers the UGR, and the highest pressure observed during the UGR.

CONCLUSION

Our results suggest that the activation of the Pcm is relevant for the UGR in male rats. Neurourol. Urodynam. 36:80-85, 2017. © 2015 Wiley Periodicals, Inc.