Administration of noradrenaline in the autonomic ganglia modifies the testosterone release from the testis using an ex vivo system

Neuropeptide Profiles of Mammalian Male Genital Tract: Distribution and Functional Relevance in Reproduction

Neuropeptides are secretory peptides characterized by small chains of amino acids linked by peptide bonds. They are majorly found in some mammalian neurons and glial cells, where they modulate a variety of physiological homeostasis. In the male genital tract, they are mostly found in the neuronal fibers supplying the vasculature, smooth muscle layer, interstitium, and lamina propria of the tunica mucosa of the various reproductive organs. Functionally, neuropeptides are strongly implicated in vascular temperature regulations, spermatozoa extrusion, epididymal content transportation, and movement of accessory gland secretions. This review provides an overview of neuropeptides with respect to their synthesis, release, and mechanism of actions, with emphasis on the locally acting neuropeptides, such as substance P (SP), neuropeptide Y (NPY), vasoactive intestinal peptides (VIP), calcitonin gene-related peptide (CGRP), galanin (GAL), cholecystokinin (CCK), C-terminal flanking peptide of NPY (CPON), peptide histidine isoleucine (PHI), and met- and leu-enkephalins (M-ENK and L-ENK) along the male genital tract (i.e., the spermatic cord, testis, epididymis, ductus deferens, and accessory sex organs) of 14 species of mammals and their marked influence on reproduction. This review also revealed from documented reports that the vast majority of neuropeptides present in the autonomic nerve supply to the male genital tract probably coexist with other peptides or with various neurotransmitters (tyrosine hydroxylase, dopamine beta hydroxylase, and 5-hydroxytryptamine). In addition, documented evidence of variation in age, season, and intraspecies differences were identified as notable factors of influence in peptidergic nerve fiber distribution.

Venlafaxine-induced adrenergic signaling stimulates Leydig cells steroidogenesis via Nur77 overexpression: a possible role of EGF

Venlafaxine, a norepinephrine and serotonin reuptake inhibitor, impairs rat sperm parameters, spermatogenesis and causes high intratesticular estrogen and testosterone levels, indicating that Leydig cells (LCs) may be a venlafaxine target. We evaluated the effect of venlafaxine treatment on LCs in vivo, focusing on adrenergic signaling, EGF immunoexpression and steroidogenesis. Germ cells mitotic/meiotic activity and UCHL1 levels were also evaluated in the seminiferous epithelium. Adult male rats received venlafaxine (30 mg/kg) or distilled water. In testicular sections, the seminiferous tubules, epithelium and the LCs nuclear areas were measured, and the immunoexpression of Ki-67, UCHL1, StAR, EGF, c-Kit and 17β-HSD was evaluated. UCHL1, StAR and EGF protein levels and Adra1a, Nur77 and Ndrg2 expression were analyzed. MDA and nitrite testicular levels, and serum estrogen and testosterone levels were measured. Venlafaxine induced LCs hypertrophy and Ndrg2 upregulation, in parallel to increased number of Ki-67, c-Kit- and 17β-HSD-positive interstitial cells, indicating that this antidepressant stimulates LCs lineage proliferation and differentiation. Upregulation of Adra1a and Nur77 could explain the high levels of StAR and testosterone levels, as well as aromatization. Enhanced EGF immunoexpresion in LCs suggests that this growth fact is involved in adrenergically-induced steroidogenesis, likely via upregulation of Nur77. Slight tubular atrophy and weak Ki-67 immunoexpression in germ cells, in association with high UCHL1 levels, indicate that spermatogenesis is likely impaired by this enzyme under supraphysiological estrogen levels. These data corroborate the unchanged MDA and nitrite levels. Therefore, venlafaxine stimulates LCs steroidogenesis via adrenergic signaling, and EGF may be involved in this process.

Nerve and Glial Cell Expressions in the Testes and Epididymides of Different Age Groups of Cane Rat (Thryonomys swinderianus)

Purpose:

This study was conducted to examine the variations in the expressions of neuronal and glial cell markers in the testes and epididymides of different age groups of cane rat using histochemical and immunohistochemical techniques.

Method:

Thirty (32) healthy domesticated male cane rats were used for this investigation. The rats were divided into four groups (prepubertal [≤4 months], pubertal (>4 ≤12 months), adult (>12 ≤30 months), and aged (>30 months)] of 8 animals each. Subsequent to anesthesia and intracardiac perfusion of the rats with 10% buffered formalin, testes were harvested and preliminary assessment of nervous and glial structures was determined using the Golgi technique. Specific immunolocalization was done using the anti-neurofilament (NF-20) and anti-glial fibrillary acid protein (GFAP) for the expressions of neuronal and astrocyte-like cells, respectively.

Result:

Neuronal and astrocyte-like structures as revealed by the Golgi procedure were demonstrated in the tunica albuginea and interstitium of the testes as well as in the periductal muscle coat and epididymal interstitium of the caput down to the caudal segments. Golgi signal intensities of the expressions in both testes and epididymides increased with age advancement. Immunolocalization of the nerve structures and glial cells tallied with the Golgi results. However, NF signal intensity was significantly higher in the adult relative to others. Similarly, GFAP signal intensity increased with age increment.

Conclusion:

This study has shown that the variation in the expression of neuronal and glial cells in the testis and epididymis of the cane rat could be associated with increased reproductive reproductive activity.

Quantification of neural and hormonal receptors at the prostate of long-term sexual behaving male rats after lesion of pelvic and hypogastric nerves

Prostate function is regulated by androgens and a neural control via the pelvic and hypogastric nerves. As such, this sexual gland contains receptors for acetylcholine and noradrenaline, although it is unknown whether the expression of these receptors is affected by sexual behavior and even less by denervation of the gland. Thus, the purpose of this work was to evaluate the effect of repeated sexual behavior on the expression of noradrenaline, acetylcholine, and androgen receptors at the prostate, and how they are affected by denervation. To achieve this, we used sexually experienced males denervated at the pelvic or hypogastric nerves, or both. The messenger (mRNA) and protein for androgen, noradrenergic, and cholinergic receptors were evaluated. The weight of the gland and the levels of serum testosterone were also measured. We found that: (1) sexual behavior was not affected by denervation; (2) blood testosterone levels increased due to sexual behavior but such increase is prevented by denervation; (3) the weight of the ventral prostate increased with sexual behavior but was not affected by denervation; (4) AR messenger levels increased with sexual behavior but were not altered by denervation; (5) the messenger for noradrenergic and cholinergic receptors decreased after denervation, and those for muscarinic receptors increased, and (6) only AR protein decreased after denervation of both nerves, while those for other receptors remained unchanged. In summary, we show that the three receptors have different regulatory mechanisms, and that only androgen receptors are regulated by both autonomic systems.

The neuroendocrine integration of environmental information, the regulation and action of testosterone and the challenge hypothesis

The authors of the original challenge hypothesis proposed influential hypotheses concerning the relationship between testosterone concentrations in the blood and aggressive social behaviors. Many of the key observations were made in avian species studied in the wild and in captivity. In this review we evaluate some remaining questions about the ideas discussed in the challenge hypothesis from a neuroendocrine perspective. For example, a rise in testosterone in response to a social aggressive stimulus might involve complex social information being processed by the brain and an appropriate signal sent to the gonadotrophin-releasing hormone (GnRH) neuronal system. Alternatively, social stimuli could more directly stimulate the testis and testosterone release via sympathetic innervation of the testis though such pathways have not been linked to a response to social behaviors. The social behavior decision network in the brain seems to play a key role in the regulation of aggressive behavior but how sensory information concerning aggressive behaviors is interpreted appropriately, processed by the social decision network and sent to the GnRH system is still not well understood. There are continuing questions about the extensive species variation in whether an increase in testosterone occurs in response to a territorial challenge, what its function might be and whether increases in testosterone are necessary to activate morphological changes, or the expression of sexual and aggressive behaviors associated with successful reproduction.

Characteristics of nobiletin-induced effects on jejunal contractility

Nobiletin, a citrus polymethoxylated flavone, exhibits multiple biological properties including anti-inflammatory, anti-carcinogenic, and anti-insulin resistance effects. The present study found that nobiletin exerted significant stimulatory effects on the contractility of isolated rat jejunal segments in all 6 different low contractile states, and meanwhile significant inhibitory effects in all 6 different high contractile states, showing characteristics of bidirectional regulation (BR). Nobiletin-exerted BR on jejunal contractility was abolished in the presence of c-kit receptor tyrosine kinase inhibitor imatinib or Ca(2+) channel blocker verapamil. In the presence of neuroxin tetrodotoxin, nobiletin only exerted stimulatory effects on jejunal contractility in both low and high contractile states. Hemicholinium-3 and atropine partially blocked nobiletin-exerted stimulatory effects on jejunal contractility in low-Ca(2+)-induced low contractile state. Phentolamine or propranolol or l-NG-nitro-arginine significantly blocked nobiletin-exerted inhibitory effects on jejunal contractility in high-Ca(2+)-induced high contractile state respectively. The effects of nobiletin on myosin light chain kinase (MLCK) mRNA expression, MLCK protein content, and myosin light chain phosphorylation extent were also bidirectional. In summary, nobiletin-exerted BR depends on the contractile states of rat jejunal segments. Nobiletin-exerted BR requires the enteric nervous system, interstitial cell of Cajal, Ca(2+), and myosin phosphorylation-related mechanisms.

Circulating testosterone and estradiol, autonomic balance and baroreflex sensitivity in middle-aged and elderly men with heart failure

BACKGROUND

Heart failure (HF) is considered as a cardiogeriatric syndrome. Its fundamental pathophysiological feature is autonomic imbalance (and associated abnormalities within cardiovascular reflex control), but recent evidence suggests the involvement of deranged hormone metabolism. Both these neural and endocrine pathologies have serious clinical and prognostic consequences in patients with HF. We investigated the relations between autonomic status, baroreflex sensitivity (BRS) and hormone status in men with mild systolic HF.

METHODS

We examined 46 men with stable systolic HF (age: 62 ± 10 years, NYHA class I/II: 10/36 [22%/78%], ischemic aetiology: 72%, left ventricular ejection fraction: 32 ± 8%). Serum hormone levels (i.e. total testosterone [TT], dehydroepiandrosterone sulphate [DHEAS], oestradiol [E2], insulin-like growth factor type 1 [IGF-1] and cortisol) were assessed using immunoassays. Estimated free testosterone (eFT) was estimated using the Vermeulen's equation. Heart rate variability (HRV) was assessed in time and frequency domains, based on 10-min resting recordings. BRS was estimated using the sequence method (BRS-Seq) and the phenylephrine test (BRS-Phe).

RESULTS

Deficiencies in circulating TT, eFT, DHEAS and IGF-1 (defined as a serum hormone ≤the 10th percentile calculated for the adequate age category in the cohort of healthy men) were found in respectively 13%, 30%, 55% and 93% of men with systolic HF. Serum SHBG ≥50 nmol/L and cortisol ≥700 nmol/L characterised, respectively 44% and 29% of men with HF. In multivariable models after the adjustment for clinical variables, the following relationships were found in examined men: DHEAS and SDNN (time domain of HRV defined as a standard deviation of average R-R intervals) (β = 0.29, p = 0.03); E2 and: HRV-LF (ms(2)) (β = 0.37, p = 0.01), HRV-HF (ms2) (β = 0.44, p = 0.02) and BRS-Phe (β = 0.51, p = 0.008); TT and: HRV-HF (%) (β = 0.35, p = 0.02), HRV-LF/HF ratio (β = -0.35, p = 0.02) and BRS-Seq (β = 0.33, p = 0.04).

CONCLUSIONS

The observed associations between reduced circulating androgens, oestrogens and lower HRV and depleted BRS, irrespectively of HF severity suggest the pathophysiological links between these two mechanisms. These results constitute the premises to investigate whether the pharmacological supplementation of depleted hormones would enable to restore the autonomic balance and improve the efficacy of reflex control within the cardiovascular system in men with systolic HF.

Involvement of the mesenteric ganglia on androstenedione, noradrenaline and nitrite release using a testis ex vivo system

The autonomic nerve fibres converge to the testis along two major pathways, the superior spermatic nerve (SSN) and the inferior spermatic nerve (ISN). The object of this work was to evaluate whether the addition of noradrenaline (NA) in the ganglionic compartment of two ex vivo systems: superior mesenteric ganglion (SMG)-SSN-testis, inferior mesenteric ganglion (IMG)-ISN-testis modulate androstenedione (A₂), NA and nitrite release and to determine whether there are secretory differences between the right and the left testis. Each gonad with its respective ganglion was transferred into a cuvette with two compartments and incubated in a Dubnoff metabolic shaker. The testis incubation liquids were collected and analysed for NA by HPLC, A₂ by RIA and nitrites by the Griess method. When NA is added to the IMG, A₂ and NA release diminishes and nitrite increases in the left testis, while in the right gonad, A₂ and NA increase and nitrite decreases. When NA was administered to the SMG, A₂ and NA increase and nitrite diminishes in the left gonad, but they show opposite fluctuations in the right testis. These ex vivo systems appear to be excellent models for studying the sympathetic ganglionic control of the testis though A₂, NA and nitrite release from the male gonad. It is evident that a better knowledge about the role of catecholamines and nitric oxide in the testis physiology may facilitate the understanding of some reproductive diseases.

Autonomic control of the urogenital tract

The urogenital tract houses many of the organs that play a major role in homeostasis, in particular those that control water and salt balance, and reproductive function. This review focuses on the anatomical and functional innervation of the kidneys, urinary ducts and bladders of the urinary system, and the gonads, gonadal ducts, and intromittent organs of the reproductive tract. The literature, especially in recent years, is overwhelmingly skewed toward the situation in mammals. Nevertheless, where specific neurochemical markers have been investigated, common patterns of innervation can be found in representatives from most vertebrate classes. Not surprisingly the vasculature, epithelia and smooth muscle of all urogenital organs receives adrenergic innervation. These nerves may contain non-adrenergic non-cholinergic (NANC) neurotransmitters such as ATP and NPY. Cholinergic nerves increase motility in most urogenital organs with the exception of the kidney. The major NANC nerves found to influence urogenital organs include those containing VIP/PACAP, galanin and neuronal nitric oxide synthase. These can be found associated with both smooth muscle and epithelia. The role these nerves play, and the circumstances where they are activated are for the most part unknown.