Influence of testosterone on the electrical properties of scrotal nerves at the cutaneous and spinal levels in the male rat

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.

Induction of Bladder Overactivity by Nerve Growth Factor in Testes in Rats: Possible Neural Crosstalk Between the Testes and Urinary Bladder

OBJECTIVES

To clarify the pathophysiological factor underlying neural crosstalk among pelvic organs, we investigated the possible role of nerve growth factor (NGF) in the neural crosstalk between the testes and urinary bladder.

METHODS

Nerve growth factor (10, 30, and 100 µg/mL) or saline was injected into the testes of male Wistar rats. The change in bladder capacity via cystometry and duration of spontaneous scratching behavior induced by NGF in conscious rats was measured. The effects of pretreatment with capsaicin on NGF-induced changes in bladder capacity and behavior were examined. Further, we evaluated the effect of analgesics, indomethacin and morphine, and pretreatment with compound 48/80 on NGF-induced scratching behavior to elucidate the mechanism of the behavior.

RESULTS

Injection of saline into the testes had no effect on bladder capacity or behavior. However, an injection of NGF (30 and 100 µg/mL) reduced bladder capacity, which was regarded as bladder overactivity, and evoked scratching behavior in a dose-dependent manner. Pretreatment with capsaicin inhibited NGF-induced bladder overactivity and scratching behavior. Neither indomethacin nor pretreatment with compound 48/80 affected the scratching behavior, but morphine inhibited the behavior.

CONCLUSIONS

The present study provides evidence of a possible new role of NGF in the testes regarding the activation of testicular primary afferent neurons mediated by capsaicin-sensitive C-fibers, which evokes bladder overactivity via neural crosstalk between the testes and the urinary bladder as well as testicular pain.

Cerebral changes after injury to the median nerve: a long-term follow up

Injury to the peripheral nerves in the upper extremity results in changes in the nerve, and at multiple sites throughout the central nervous system (CNS). We studied the long-term effects of an injury to the median nerve in the forearm with a focus on changes in the CNS. Four patients with isolated injuries of the median nerve in their 20s were examined a mean of 14 years after the injury. Cortical activation was monitored during tactile stimulation of the fingers of the injured and healthy hand using functional magnetic resonance imaging at 3 Tesla. The neurophysiological state and clinical outcome were also examined. Activation in the primary somatosensory cortex was substantially larger during tactile stimulation of the injured hand than with stimulation of the uninjured hand. We also saw a redistribution of hemispheric dominance. Stimulation of the injured median nerve resulted in a substantially increased dominance of the contralateral hemisphere. However, stimulation of the healthy ulnar nerve resulted in a decreased dominance of the contralateral hemisphere. Neurophysiology showed low sensory amplitudes, velocity, and increased motor latency in the injured nerve. Clinically there were abnormalities predominately in the sensory domain. However, there was an overall improved mean result compared with a five year follow-up in the same subjects. The cortical changes could be the result of cortical reorganisation after a changed afferent signal pattern from the injured nerve. Even though the clinical function improved over time it did not return to normal, and neither did the cortical response.

Histological modifications of the rat prostate following transection of somatic and autonomic nerves

It is known that hormones influence significantly the prostate tissue. However, we reported that mating induces an increase in androgen receptors, revealing a neural influence on the gland. These data suggested that somatic afferents (scrotal and genitofemoral nerves) and autonomic efferents (pelvic and hypogastric nerves) could regulate the structure of the prostate. Here we assessed the role of these nerves in maintaining the histology of the gland. Hence, afferent or efferent nerves of male rats were transected. Then, the ventral and dorsolateral regions of the prostate were processed for histology. Results showed that afferent transection affects prostate histology. The alveoli area decreased and increased in the ventral and dorsolateral prostate, respectively. The epithelial cell height increased in both regions. Efferent denervation produced dramatic changes in the prostate gland. The tissue lost its configuration, and the epithelium became scattered and almost vanished. Thus, afferent nerves are responsible for spinal processes pertaining to the trophic control of the prostate, activating its autonomic innervation. Hence, our data imply that innervation seems to be synergic with hormones for the healthy maintenance of the prostate. Thus, it is suggested that some prostate pathologies could be due to the failure of the autonomic neural pathways regulating the gland.

Identification of perineal sensory neurons activated by innocuous heat

C-fiber sensory neurons comprise nociceptors and smaller populations of cells detecting innocuous thermal and light tactile stimuli. Markers identify subpopulations of these cells, aiding our understanding of their physiological roles. The transient receptor potential vanilloid 1 (TRPV1) cation channel is characteristic of polymodal C-fiber nociceptors and is sensitive to noxious heat, irritant vanilloids, and protons. By using immunohistochemistry, in situ hybridization, and retrograde tracing, we anatomically characterize a small subpopulation of C-fiber cells that express high levels of TRPV1 (HE TRPV1 cells). These cells do not express molecular markers normally associated with C-fiber nociceptors. Furthermore, they express a unique complement of neurotrophic factor receptors, namely, the trkC receptor for neurotrophin 3, as well as receptors for neurturin and glial cell line-derived neurotrophic factor. HE TRPV1 cells are distributed in sensory ganglia throughout the neuraxis, with higher numbers noted in the sixth lumbar ganglion. In this ganglion and others of the lumbar and sacral regions, 75% or more of such HE TRPV1 cells express estrogen receptor alpha, suggestive of their regulation by estrogen and a role in afferent sensation related to reproduction. Afferents from these cells provide innervation to the hairy skin of the perineal region and can be activated by thermal stimuli from 38 degrees C, with a maximal response at 42 degrees C, as indicated by induction of extracellular signal-regulated kinase phosphorylation. We hypothesize that apart from participating in normal thermal sensation relevant to thermoregulation and reproductive functions, HE TRPV1 cells may mediate burning pain in chronic pain syndromes with perineal localization.

Behavioral and urological evaluation of a testicular pain model

OBJECTIVES

To develop an animal model of testicular pain to examine the hypothesis that neural crosstalk between testicular nociceptors and bladder reflex pathways may underlie bladder overactivity. In chronic pelvic pain disorders, neural crosstalk is thought to underlie referred pain and functional interaction in pelvic organs, and patients with chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) suffer from pain in multiple organs, including the testes and perineum, as well as increased urinary frequency.

METHODS

In male Wistar rats, acetic acid was injected into the testes, and behaviors and bladder functions with conscious cystometry were examined. The effects of indomethacin and capsaicin pretreatment on both behaviors and bladder functional changes induced by acetic acid injection were examined. The weight of the testes and bladder after the testicular injection were measured.

RESULTS

Injection of acetic acid (1% and 3%) induced pain behaviors and bladder overactivity proportional to the concentration. Indomethacin reduced, and capsaicin pretreatment almost completely abolished, both pain behavior and bladder overactivity induced by acetic acid injection. Administration of acetic acid increased testis weight and blanched the tissue, but no apparent changes were observed in the bladder.

CONCLUSIONS

Injection of dilute acetic acid into the testes produces a reproducible testicular pain model involving testicular inflammation and activation of primary afferent C fibers and suggests a neural pathway for interaction between testicular pain and bladder overactivity. This study may provide a simple method to evaluate testicular pain, related bladder overactivity, and insight into the pathophysiology of bladder overactivity in patients with CP/CPPS.

Characteristics of ejaculated rat semen after lesion of scrotal nerves

The scrotum, representing the pouch surrounding the testes and their associated structures, plays a significant role in maintaining the gonad at a temperature lower than that of the body. Although thermoregulation of the testes has been ascribed as a main function of the scrotum, here we found that mechanical stimulation of the scrotum is important during mating to facilitate the appropriate expulsion of semen during ejaculation. Previously we showed that the scrotal skin area is innervated by two nerve branches, the proximal (Psb) and distal (Dsb) scrotal branches which supply the proximal or distal half of the scrotum, respectively. The sensory field of each nerve is testosterone-dependent. The decreased androgen levels following castration reduce the sensitive area to mechanical stimuli that can be restored following exogenous administration of the hormone. Here, we tested the effect of scrotal nerve transection on sexual parameters of experienced male rats. Data show that lesion of PSb or DSb alone or combined did not affect the execution of sexual behavior. However, these lesions significantly reduced the proportion of males that expelled semen during ejaculation, with that semen showing a reduced quantity of sperm. Thus, scrotal nerves are important in reproduction not for the appropriate display of sexual behavior, but for the expulsion of a normal quantity of semen and number of sperm during ejaculation. Our suggestion is that scrotal afferents trigger spinal reflexes to activate autonomic efferents supplying the male reproductive tract for the control of seminal emission.

A study of the prostate, androgens and sexual activity of male rats

BACKGROUND

The prostate is a sexual gland that produces important substances for the potency of sperm to fertilize eggs within the female reproductive tract, and is under complex endocrine control. Taking advantage of the peculiar behavioral pattern of copulating male rats, we developed experimental paradigms to determine the influence of sexual behavior on the level of serum testosterone, prostate androgen receptors, and mRNA for androgen receptors in male rats displaying up to four consecutive ejaculations.

METHODS

The effect of four consecutive ejaculations was investigated by determining levels of (i) testosterone in serum by solid phase RIA, (ii) androgen receptors at the ventral prostate with Western Blots, and (iii) androgen receptors-mRNA with RT-PCR. Data were analyzed with a one-way ANOVA followed by a post hoc application of Dunnett's test if required.

RESULTS

The constant execution of sexual behavior did not produce any change in the weight of the ventral prostate. Serum testosterone increased after the second ejaculation, and remained elevated even after four ejaculations. The androgen receptor at the ventral prostate was higher after the first to third ejaculations, but returned suddenly to baseline levels after the fourth ejaculation. The level of mRNA increased after the first ejaculation, continued to increase after the second, and reached the highest peak after the third ejaculation; however, it returned suddenly to baseline levels after the fourth ejaculation.

CONCLUSION

Four consecutive ejaculations by sexually experienced male rats had important effects on the physiological responses of the ventral prostate. Fast responses were induced as a result of sexual behavior that involved an increase and decrease in androgen receptors after one and four ejaculations, respectively. However, a progressive response was observed in the elevation of mRNA for androgen receptors, which also showed a fast decrease after four ejaculations. All of these changes with the prostate gland occurred in the presence of a sustained elevation of testosterone in the serum that started after two ejaculations. A consideration of these fast-induced changes suggests that the nerve supply plays a key role in prostate physiology during the sexual behavior of male rats.

Pattern of sensory innervation of the perineal skin in the female rat

Here we describe the nerves innervating the perineal skin together with their sensory fields in the adult female rat. Electrophysiological recording showed that the lumbosacral and L6-S1 trunks, in part by way of the sacral plexus, transmit sensory information from the perineal skin via four nerves: the viscerocutaneous branch of the pelvic nerve innervating the skin at the midline between the vaginal opening and anus, the sensory branch of the pudendal nerve innervating the clitoral sheath, the distal perineal branch of the pudendal nerve innervating a broad area of skin adjacent to the vaginal opening and anus, and the proximal perineal branch of the sacral plexus innervating a broad area of skin adjacent to the clitoris and vaginal opening. The sensory fields of three of these nerves overlapped to some degree: the viscerocutaneous branch of the pelvic and the distal perineal branch of the pudendal nerves at the midline skin between the vaginal opening and the anus, and the distal perineal branch of the pudendal nerve and the proximal perineal branch of the sacral plexus at the skin lateral to the vaginal opening. Such overlap might provide a safeguard helping to ensure that somatosensory input from the perineal region important for triggering reproductive and nonreproductive reflexes reaches the CNS.