Influence of Testosterone Depletion on Neurotrophin-4 in Hippocampal Synaptic Plasticity and Its Effects on Learning and Memory.

Sex steroids are neuromodulators that play a crucial role in learning, memory, and synaptic plasticity, providing circuit flexibility and dynamic functional connectivity in mammals. Previous studies indicate that testosterone is crucial for neuronal functions and required further investigation on various frontiers. However, it is surprising to note that studies on testosterone-induced neurotrophin-4 (NT-4) expression and its influence on synaptic plasticity and learning and memory moderation are scanty. The present study is focused on analysing the localized influence of NT-4 on hippocampal synaptic plasticity and associated moderation in learning and memory under testosterone deprivation. Adult Wistar albino rats were randomly divided into various groups, control (Cont), orchidectomy (ORX), ORX + testosterone supplementation (ORX + T), and Cont + testosterone (Cont + T). After 2 weeks, the serum testosterone level was undetectable in ORX rats. The behavioural assessment showed a decline in the learning ability of ORX rats with increased working and reference memory errors in the behavioural assessment in the 8-arm radial maze. The mRNA and protein expressions of NT-4 and androgen receptors (ARs) were significantly reduced in the ORX group. In addition, there was a decrease in the number of neuronal dendrites in Golgi-Cox staining. These changes were not seen in ORX + T rats with improved learning behaviour indicating that testosterone exerts its protective effect on hippocampal synaptic plasticity through AR-dependent NT-4 regulation in learning and memory upgrade.

Testosterone Influence on Microtubule-Associated Proteins and Spine Density in Hippocampus: Implications on Learning and Memory.

The thorny protrusions or spines increase the neuronal surface area, facilitate synaptic interconnections among neurons, and play an essential role in the hippocampus. Increasing evidence suggests that testosterone, the gonadal hormone, plays an important role in neurogenesis and synaptic plasticity. The role of testosterone on microtubule-associated proteins on dendritic neurite stability in the hippocampus and its impact on learning disability is not elucidated. Adult male Wistar albino rats were randomly selected for the control, castrated, castrated + testosterone, and control + testosterone groups. Bilateral orchidectomy was done, and the testosterone propionate was administered during the entire trial period, i.e., 14 days. The learning assessments were done using working/reference memory versions of the 8-arm radial maze and hippocampal tissues processed for histological and protein expressions. There were reduced expressions of microtubule-associated protein 2 (MAP2), postsynaptic density protein 95 (PSD95), and androgen receptor (AR) and increased expression of pTau in the castrated group. Conversely, the expression of MAP2, PSD95, and AR was increased, and the pTau expression was reduced in the hippocampus of the castrated rat administrated with testosterone. Androgen-depleted rats showed impaired synaptic plasticity in the hippocampus associated with contracted microtubule dynamics. Along with learning disability, there was an increased number of reference memory errors and working memory errors in castrated rats. Observations suggest that androgen regulates expression of neural tissue-specific MAPs and plays a vital role in hippocampus synaptic plasticity and that a similar mechanism may underlie neurological disorders in aging and hypogonadal men.

Apoptosis in hippocampal tissue induced by oxidative stress in testosterone deprived male rats.

The testosterone decline is one of the potential causes of oxidative stress-induced anxiety and depressive behaviors, and cognitive impairment induces irreversible neuronal damage, which is not clearly understood. The orchidectomized rat model was used; the hippocampal neurons and anxiety behavior were analyzed. Adult male albino rats were divided into control and orchidectomy (ORX) groups, orchidectomy (ORX + T), and normal (Cont + T) groups. Testosterone propionate was used as a testosterone supplement. The anxiety and depressive-like behavior observed in ORX animals in the open field (OF) and elevated plus-maze experiments were effectively overturned in the ORX + T group. Studies on isolated hippocampus showed reduced antioxidant enzymes (SOD, CAT, and glutathione (GSH) compounds), increased lipid peroxidation (LPO), elevated caspase3, and reduced anti-apoptotic protein Bcl-2, and increased apoptotic nuclei in TUNEL staining of the hippocampus in the ORX rats. These observations indicate free radical-mediated neural damage. Testosterone presence promoted the antioxidant defense system and restored normal pyramidal neuron morphology in ORX + T. This study confirms that testosterone is indispensable in the normal adult hippocampus and deficiency seems to be a potential risk factor for neurodegenerative disorders. Besides, androgen appears to be a possible therapeutic strategy for treating depression/neurodegenerative diseases in aging men.

Pathobiology of ischiocavernosus and bulbospongiosus muscles in long-term diabetic male rats and its implication on erectile dysfunction.

OBJECTIVE: To analyze pathobiology of ischiocavernosus (IC) and bulbospongiosus (BS) muscles in long-term diabetic male rats and its implication on erectile dysfunction (ED). METHODS: Male rats were grouped into control and diabetic rats (received single injection of 60 mg/kg bw. of streptozotocin [STZ]). At 120th day, the animals were subjected to various analyses like serum hormone, penile reflex, electromyography of IC and BS muscles, after euthanasia IC and BS muscles were processed for morphological, histology, histometric analysis, immunostaining and immunoblotting synaptophysin, nNOS and NADPH diaphorase histochemistry. RESULTS: Significant reduction in serum hormone level, penile reflex, reduced action potential or activity in both these muscles and wide range of histological alterations were observed in STZ rats. Muscles showed significant reduction in the diameter, volume and numerical density of the fiber in both muscles of STZ rats. Synaptophysin, nNOS and NADPH diaphorase were significantly reduced in diabetic animal IC and BS. CONCLUSION: Severe neuromuscular circuitry alteration in IC and BS. Study concludes that degenerative changes in IC and BS may play a major role in ED in diabetic condition. Indicating diabetic-induced postsynaptic neuronal degeneration along with impaired motor action of the muscle and severe muscle degeneration affecting ED.

Therapeutic potential of Mucuna pruriens (Linn.) on ageing induced damage in dorsal nerve of the penis and its implication on erectile function: an experimental study using albino rats.

OBJECTIVE: To study the effect of ethanolic seed extract of Mucuna pruriens on damaged dorsal nerve of the penis (DNP) in aged rat in relation to penile erection. METHODS: The rats were divided into four groups Young (3 months), Aged (24 - 28 months), Aged + M. pruriens, and Young + M. pruriens (200 mg/kg b.w/60 days) and were subjected to the hypophysial - gonadal axis, nerve conduction velocity (NCV), and penile reflex. DNP sections were stained with nitric oxide synthase (nNOS), nicotinamide adenine dinucleotide phosphate (NaDPH) diaphorase, androgen receptor (AR), and osmium tetroxide. Terminal deoxynucleotidyl transferase (TdT) dUTP Nick-End Labeling (TUNEL) staining, electron microscopy(EM) and histometric analyses were done. RESULTS: Significant disturbance in hypophysial - gonadal axis was noted in aged rat. With reduced number of myelinated fibers, diameter, vacuolization, indentation of the myelin sheath, and degeneration. nNOS and its cofactor (NaDPH diaphorase) were reduced in aged rat DNP. NCV was slow in aged rats and concomitant poor penile reflex was also noted. AR showed reduced expression in aged rat DNP when compared to young and control groups. TUNEL positive cells were increased in aged rat DNP. These pathological changes were remarkably reduced or recovered in M. pruriens treated aged rats. CONCLUSIONS: The results indicate a multi-factorial therapeutic activity in penile innervations towards sustaining the penile erection in the presence of the extract in aged rats and justifying the claim of traditional usage.

Therapeutic potential of Mucuna pruriens (Linn.) on high-fat diet-induced testicular and sperm damage in rats.

Objective: Mucuna pruriens Linn., a leguminous plant, is identified as a herbal medicine for improving fertility-related disorders in the alternative and complementary systems of medicine. The study was focused on evaluating the therapeutic potential of M. pruriens on testis and sperm parameters in a high-fat-induced hypercholesterolemia model. Materials and Methods: Male rats were divided as normal-control rats (NCR); normal-control rats + M.pruriens (200 mg/kg b.w. of ethanolic extract of M. pruriens seed) treated (NCRD); hypercholesterolemic rats (HCR) and hypercholesterolemic rats + M. pruriens (HCRD). Groups were further divided into three post-exposure periods (subgroups) of 9, 18, and 36 days, and the progressive changes in testis histology and sperm were analyzed. Results: The study showed a significant impairment in testicular histoarchitecture, depletion of antioxidant enzyme levels, increased oxidative stress and lipid peroxidation in the HCR group. The study indicated severe structural and functional damage in sperm parameters and diminished chromatin integrity in the HCR group. In the HCR rats, the follicular stimulating hormone (FSH) and luteinizing hormone (LH) and testosterone were significantly reduced. There was a significant improvement in sperm parameters and testis histology in the HCRD group. Conclusion: The study reveals the potential efficacy of M. pruriens to improve spermatogenesis, sperm parameters and hormone levels in hypercholesterolemic rats.

Expression of adenosine receptors and vegf during angiogenesis and its inhibition by pentoxifylline-A study using zebrafish model.

Angiogenesis, formation of new blood vessels is an important process involved in neovascular diseases and tumor progression. Understanding and defining novel therapeutic targets of neovascular diseases like retinopathy of prematurity, diabetic retinopathy and age-related macular degeneration have been hindered by a lack of appropriate animal models. Zebrafish provides an excellent vertebrate model to study above disorders since its circulatory system and retinal layers are similar to mammals. Adenosine is a known mediator of angiogenesis in hypoxic condition and adenosine receptor antagonists such as theophylline, theobromine are known to exert antiangiogenic properties. We evaluated the anti-angiogenic potential of a methylxanthine pentoxifylline (PTX) with various concentrations (0.1-1mM) at 50% epiboly stage (5.2 hpf) of zebrafish embryos and studied the mRNA expression of major angiogenic factors like vegfaa and its receptors under normal conditions and when treated with an adenosine analog NECA (5'-N-ethylcarboxamidoadenosine). Upregulation of adenosine receptors, hif-1α and vegfaa by NECA could possibly mimic hypoxic condition, but PTX downregulated vegfaa and other growth factors at 1mM concentration. Vegfa protein expression was also downregulated by PTX in the retina and the compound did not damage the retinal cells. Embryos treated with PTX generated abnormal phenotypic variants with poor vasculature, tail bending and developmental delay at 1mM. Survival rates, heart rate and hatching rates were also significantly lower. Targeting the vegf signaling pathway with small molecules inhibiting adenosine receptors in addition to antagonizing vegf might be a promising approach to treat neovascular diseases of the retina and also tumors.

Long-term study of vasectomy in Macaca radiata--histological and ultrasonographic analysis of testis and duct system.

This study was aimed to investigate the long-term effect of vasectomy using the bonnet monkey (Macaca radiata) as a primate animal model. Animals weighing around 6 to 8 kg were randomly chosen for bilateral, unilateral vasectomy and sham-control. The postoperative periods of six months and two years were considered as short and long-term, respectively. Sperm were collected and subjected to analysis before euthanasia. The testes and epididymides were excised from euthanized animals then embedded in paraffin. Normal histological changes were observed in sham-operated animals and short-term contralateral testes. In contrast, marked alterations were observed in the testes and epididymides of both short and long-term groups. Seminiferous epithelium was thinned out showing marked depletion of germ cells in long-term; only a thin layer of Sertoli cells, spermatogonia, and fewer spermatocytes were seen. Exfoliation of germ cells and the occurrence of multinucleated giant cells were common features in these tubules. The epididymal tubular lumens were greatly dilated with accumulated spermatozoa in short and long-term animals; significant defects were observed in the epithelium of the long-term animals. Microscopic spermatic granulomas were noticed in epididymides and the vas deferens. Large granulomas were seen in long-term vasectomized monkeys, frequently compressing the surrounding structures. These granulomas could be visualized in ultrasound, however, only at the late stage of its occurrence. Sperm collected from the unilateral vasectomized animals showed a poor motility score in the capillary mucus penetration test (CMPT). Results indicate that the changes observed after vasectomy might be due to pressure initially, whereas in the long-term the damage was supplemented by autoimmune attack. With immunoglobulin (IgG) deposition in contra-lateral unoperated testis of unilateral vasectomized animals it also showed degenerative changes and a concomitant drop in sperm quality. Although, granulomatous reactions were observed in the epididymis and vas deferens but testes were spared from such reactions even in the long-term.