Sex differences in the stereological parameters of the hippocampal dentate gyrus of the guinea-pig before puberty

Physical and chemical characterization of the femur during and after the body development period in male and female guinea pigs

In this study, it was aimed to reveal the physical and chemical characterization of the bone structures during body development periods (prepubertal period, period between adolescence and adulthood) and after (young adult period and old adult period) in male and female guinea pigs. In this study, 40 guinea pigs (20 male, 20 female) were used. Morphometric measurements, X-ray fluorescence (XRF) analysis for mineral levels, Brunauer-Emmett-Teller (BET) analysis for surface area, and porosity analysis were applied to the bones. The male guinea pigs had greater values than females in the other three categories, with the exception of the second group, when the females have higher values in morphometric measurements. Ca levels rose up to the third group, as did P levels in the males, peaking in the third group and declining in the fourth. As with phosphorus, there was a progressive rise in females from the first to the fourth group. Fe, Zn, and Sr elements had the greatest values in both genders in the first group. In all four groups, the females had greater Zn levels than males. The highest Ca/P ratio was found in the third male group and the fourth female group. This study revealed that adolescence, adulthood, and gender are effective in the physical and chemical characterization of bone structure in guinea pigs.

Association between nandrolone and behavioral alterations: A systematic review of preclinical studies

BACKGROUND AND AIM

In recent years the expanding misuse of Nandrolone among non-athletes, particularly adolescent males is a prevalent global concern due to its adverse effects. This article provides a summary of the experimental studies to clarify the relationship between Nandrolone exposure and behavioral and cognitive performances.

MATERIALS AND METHODS

The present systematic review was conducted using PubMed, Embase and ScienceDirect databases, from 2000 to 2020, using the following key terms: Nandrolone AND Cognition, Nandrolone AND Learning, Nandrolone AND Memory, Nandrolone AND (Synaptic plasticity or Hippocampal synaptic plasticity), Nandrolone AND (Aggression or Aggressive-like behavior), Nandrolone AND (Anxiety or Anxiety-like behavior), Nandrolone AND (Depression or Depressive-like behavior).

RESULTS

33 qualified papers were selected from the 2498 sources found. Of the 33 cases, 32 (96.97%) were males while only 1 (3.03%) was female and male. From 33 selected articles 8 reported studies were related to spatial memory, 2 reported studies were related to avoidance memory, 11 studies reported information on synaptic plasticity, 11 reported studies were related to aggressive behavior, 8 reported studies were related to aggressive behavior and 6 reported studies were related to depression.

CONCLUSION

Nandrolone can change spatial ability, avoidance memory and hippocampal synaptic plasticity. Also, Nandrolone exposure produces variable effects on behavioral function such as aggression, depression and anxiety. This despite the fact that the results are contradictory. These discrepancies might be due to the differences in sex, age, dosage and treatment duration, and administration route. However, the negative results are more common than the published positive ones.

The flavonoid 7,8-DHF fosters prenatal brain proliferation potency in a mouse model of Down syndrome

Neurogenesis impairment is a key determinant of intellectual disability in Down syndrome (DS), a genetic pathology due to triplication of chromosome 21. Since neurogenesis ceases after birth, apart in the hippocampus and olfactory bulb, the only means to tackle the problem of neurogenesis impairment in DS at its root is to intervene during gestation. A few studies in DS mouse models show that this is possible, although the drugs used may raise caveats in terms of safety. We previously found that neonatal treatment with 7,8-dihydroxyflavone (7,8-DHF), a flavonoid present in plants, restores hippocampal neurogenesis in the Ts65Dn model of DS. The goal of the current study was to establish whether prenatal treatment with 7,8-DHF improves/restores overall brain proliferation potency. Pregnant Ts65Dn females received 7,8-DHF from embryonic day 10 until delivery. On postnatal day 2 (P2) the pups were injected with BrdU and were killed after either 2 h or 52–60 days (P52–60). Evaluation of the number of proliferating (BrdU+) cells in various forebrain neurogenic niches of P2 mice showed that in treated Ts65Dn mice proliferation potency was improved or even restored in most of the examined regions, including the hippocampus. Quantification of the surviving BrdU+ cells in the dentate gyrus of P52–60 mice showed no difference between treated and untreated Ts65Dn mice. At P52–60, however, treated Ts65Dn mice exhibited a larger number of granule cells in comparison with their untreated counterparts, although their number did not reach that of euploid mice. Results show that 7,8-DHF has a widespread impact on prenatal proliferation potency in Ts65Dn mice and exerts mild long-term effects. It remains to be established whether treatment extending into the neonatal period can lead to an improvement in brain development that is retained in adulthood.

Calcineurin is involved in retrieval of passive avoidance memory and synaptic plasticity impairment induced by Nandrolone administration in adolescent male rats

In spite of evidence about negative effects of Nandrolone Decanoate (ND) on cognitive and memory performance, the underlying mechanisms are complex and have remained unclear. This research examines the role of Calcineurin in synaptic plasticity and memory storage impairment in ND administrated adolescent male rats. For behavioral study by passive avoidance learning and memory (PAL), adolescent male rats were treated with ND or ND plus selective Calcineurin antagonist (Tacrolimus), before retention test. ND significantly decreased the retrieval of PAL, whereas Tacrolimus plus ND had no significant effect on PAL. For electrophysiological study hippocampal slices were perfused by ND or ND plus Tacrolimus. The magnitude of fEPSP-LTP of ND perfused slices was less than the control and a reduction of fEPSP-PS (E-S) coupling was observed, while pre-administration of Tacrolimus abolished the ND impairment effect on fEPSP-LTP and E-S coupling. This study showed that ND may induce impairing effects on hippocampal area CA1 activity and plasticity and PAL memory storage through changes in the function of the Calcineurin.

Nandrolone administration abolishes hippocampal fEPSP-PS potentiation and passive avoidance learning of adolescent male rats

Despite the chronic effects of nandrolone decanoate (ND), the acute effects of ND on passive avoidance learning (PAL) and memory and its mechanism have not been investigated. This research examines the acute effect of ND on PAL, CA1 synaptic plasticity, testosterone and corticosterone serum levels, and the role of androgenic receptors (ARs). Adolescent male rats were treated with ND, 30 min before training and retention and after training test. AR antagonist was applied 15 min before ND. Hippocampal slices were perfused by ND. ND administration had an inverted U-shape effect on acquisition of PAL and on testosterone and corticosterone serum levels. The consolidation was only affected by high dose of ND. ND significantly decreased the retention of PAL across all doses. The magnitude of field excitatory postsynaptic potential long term potentiation was lower than that of control slices. In addition, an attenuation of field excitatory postsynaptic potential population spike coupling was also observed. Nilutamide could nullify the ND impairment effect. We concluded although a single dose of ND could affect all stages of PAL, its effects were more potent on retrieval, possibly arising from the acute effect of ND on the alterations of CA1 synaptic plasticity. In addition, ND may induce its effects directly through ARs and indirectly through plasma testosterone and corticosterone.

Histopathological analysis of the olfactory epithelium of zebrafish (Danio rerio) exposed to sublethal doses of urea

Chronic renal disease is known to alter olfactory function, but the specific changes induced in olfactory organs during this process remain unclear. Of the uraemic toxins generated during renal disease, high levels of urea are known to induce hyposmic conditions. In this study, the effects of environmental exposure to elevated concentrations of urea (7, 13.5 and 20 g L(-1)) on the sensory mucosa of zebrafish in acute toxicity and chronic toxicity tests were described. It was observed that lamellae maintained structural integrity and epithelial thickness was slightly reduced, but only following exposure to the highest concentrations of urea. Pan-neuronal labelling with anti-Hu revealed a negative correlation with levels of urea, leading to investigation of whether distinct neuronal subtypes were equally sensitive. Using densitometric analysis of immunolabelled tissues, numbers of Gα olf-, TRPC2- and TrkA-expressing cells were compared, representing ciliated, microvillous and crypt neurons, respectively. The three neuronal subpopulations responded differently to increasing levels of urea. In particular, crypt cells were more severely affected than the other cell types, and Gα olf-immunoreactivity was found to increase when fish were exposed to low doses of urea. It can be concluded that exposure to moderate levels of urea leads to sensory toxicity directly affecting olfactory organs, in accordance with the functional olfactometric measurements previously reported in the literature.

Pharmacological and methodological aspects of the separation-induced vocalization test in guinea pig pups; a systematic review and meta-analysis

The separation-induced vocalization test in guinea pig pups is one of many that has been used to screen for anxiolytic-like properties of drugs. The test is based on the cross-species phenomenon that infants emit distress calls when placed in social isolation. Here we report a systematic review and meta-analysis of pharmacological intervention in the separation-induced vocalization test in guinea pig pups. Electronic databases were searched for original research articles, yielding 32 studies that met inclusion criteria. We extracted data on pharmacological intervention, animal and methodological characteristics, and study quality indicators. Meta-analysis showed that the different drug classes in clinical use for the treatment of anxiety disorders, have comparable effects on vocalization behaviour, irrespective of their mechanism of action. Of the experimental drugs, nociception (NOP) receptor agonists proved very effective in this test. Analysis further indicated that the commonly used read-outs total number and total duration of vocalizations are equally valid. With regard to methodological characteristics, repeated testing of pups as well as selecting pups with moderate or high levels of vocalization were associated with larger treatment effects. Finally, reporting of study methodology, randomization and blinding was poor and Egger's test for small study effects showed that publication bias likely occurred. This review illustrates the value of systematic reviews and meta-analyses in improving translational value and methodological aspects of animal models. It further shows the urgent need to implement existing publication guidelines to maximize the output and impact of experimental animal studies.

The effects of season and sex on dentate gyrus size and neurogenesis in a wild rodent, Richardson's ground squirrel (Urocitellus richardsonii)

Sex and reproductive status affect hippocampal neurogenesis and dentate gyrus (DG) size in rodents. Relatively few studies, however, address these two effects simultaneously and even fewer studies address this issue in wild populations. Here, we examined seasonal and sex differences in neurogenesis and DG size in a wild, polygynous and social rodent, Richardson's ground squirrel (Uriocitellus richardsonii). Based on the behavioral ecology of this species, we predicted that both neurogenesis and DG size would be sexually dimorphic and the degree of dimorphism would be greatest in the breeding season. Using unbiased stereology and doublecortin (DCX) immunohistochemistry, we found that brain volume, DG size and number of DCX cells varied significantly between breeding and non-breeding seasons, but only brain volume and the number of DCX labeled cells differed between the sexes. Both sex and seasonal differences likely reflect circulating hormone levels, but the extent to which these differences relate to space use in this species is unclear. Based on the degree of seasonal differences in neurogenesis and the DG, we suggest that ground squirrels could be considered model species in which to examine hippocampal plasticity in an ecologically valid context.

Postnatal neurogenesis in the hippocampal dentate gyrus and subventricular zone of the Göttingen minipig

Postnatal neurogenesis is currently viewed as important for neuroplasticity and brain repair. We are, therefore, interested in animal models for neuroimaging of postnatal neurogenesis. A recent stereological study found an age-dependent increase in the number of neurons and glial cells in the neocortex of Göttingen minipigs, suggesting that this species may be characterized by a prolonged postnatal neurogenesis. Since there is no direct evidence on this issue, the goal of our study was to quantify cell proliferation in the two major neurogenic regions of the postnatal brain - the subventricular zone of the lateral ventricle (SVZ) and the hippocampal dentate gyrus (DG) - at two separate points during the lifespan of the minipig. Göttingen minipigs aged 6-7 and 32 weeks were injected with bromodeoxyuridine (BrdU), a marker of cycling cells, and killed after 2h. We found BrdU-positive cells numbering 165,000 in the SVZ and 35,000 in the DG at 6-7 weeks and 66,000 in the SVZ and 19,000 in the DG at 32 weeks-of-age. Stereology showed a 60% increase in the total number of DG granule cells between 6-7 and 32 weeks-of-age. Our findings show a continued postnatal neurogenesis in the major neurogenic regions of Göttingen minipigs, thereby providing a potential animal model for studies aimed at examining ongoing neurogenesis in the living brain with molecular neuroimaging technology.

Patterns of brain activation during visually evoked sexual arousal differ between homosexual and heterosexual men

BACKGROUND AND PURPOSE

Nowadays the mechanism of homosexuality is little known. Few studies have been carried out to explore the brain functional changes of homosexual men during sexual arousal. We used functional MR imaging (fMRI) to determine whether the patterns of brain activation in homosexual and heterosexual men differed during visually evoked sexual arousal.

MATERIALS AND METHODS

To all the subjects (10 homosexual and 10 heterosexual), real-time visual stimulation was provided by 3-minute exposure to 3 types of erotic film: heterosexual couples (F-M), male homosexual couples (M-M), and female homosexual couples (F-F) engaged in sexual activity, during which time fMRI was used to determine the patterns of brain activation. Self-reports of level of sexual arousal were collected immediately afterward.

RESULTS

Statistical parametric mapping showed that viewing erotic film excerpts that induced sexual arousal was associated, in both groups, with activation of the middle prefrontal gyrus, bilateral temporal lobe and postcentral gyrus, thalamus, insula, vermis, left precuneus, occipital cortex, parietal cortex, and cerebellum. In homosexual men, the left angular gyrus, left caudate nucleus, and right pallidum were activated; in contrast, heterosexual men showed no activation in these regions. However, heterosexual men showed activation in the bilateral lingual gyrus, right hippocampus, and right parahippocampal gyrus, areas not activated in homosexual men. In both groups, region-of-interest analysis revealed no correlation between the magnitude of amygdala or thalamus activation and the reported level of sexual arousal.

CONCLUSION

Our findings indicate that different neural circuits are active during sexual arousal in homosexual and heterosexual men and may contribute to a better understanding of the neural basis of male sexual orientation.

Methylphenidate administration to juvenile rats alters brain areas involved in cognition, motivated behaviors, appetite, and stress

Thousands of children receive methylphenidate (MPH; Ritalin) for attention deficit/hyperactivity disorder (ADHD), yet the long-term neurochemical consequences of MPH treatment are unknown. To mimic clinical Ritalin treatment in children, male rats were injected with MPH (5 mg/kg) or vehicle twice daily from postnatal day 7 (PND7)-PND35. At the end of administration (PND35) or in adulthood (PND135), brain sections from littermate pairs were immunocytochemically labeled for neurotransmitters and cytological markers in 16 regions implicated in MPH effects and/or ADHD etiology. At PND35, the medial prefrontal cortex (mPFC) of rats given MPH showed 55% greater immunoreactivity (-ir) for the catecholamine marker tyrosine hydroxylase (TH), 60% more Nissl-stained cells, and 40% less norepinephrine transporter (NET)-ir density. In hippocampal dentate gyrus, MPH-receiving rats showed a 51% decrease in NET-ir density and a 61% expanded distribution of the new-cell marker PSA-NCAM (polysialylated form of neural cell adhesion molecule). In medial striatum, TH-ir decreased by 21%, and in hypothalamus neuropeptide Y-ir increased by 10% in MPH-exposed rats. At PND135, MPH-exposed rats exhibited decreased anxiety in the elevated plus-maze and a trend for decreased TH-ir in the mPFC. Neither PND35 nor PND135 rats showed major structural differences with MPH exposure. These findings suggest that developmental exposure to high therapeutic doses of MPH has short-term effects on select neurotransmitters in brain regions involved in motivated behaviors, cognition, appetite, and stress. Although the observed neuroanatomical changes largely resolve with time, chronic modulation of young brains with MPH may exert effects on brain neurochemistry that modify some behaviors even in adulthood.

Sex differences in the hilar mossy cells of the guinea-pig before puberty

Numerous sex differences have been detected in the morphology of the dentate and hippocampal neurons and hippocampus-dependent memory functions. The aim of the present study was to ascertain whether the mossy cells, an interneuron population forming a recurrent excitatory circuit with the dentate granule cells, are sexually dimorphic. The brains of juvenile (15-16 days old) and peripubescent (45-46 days old) male and female guinea-pigs were Golgi-Cox stained. Mossy cells were sampled from the hilus in the septal third of the dentate gyrus and their dendritic tree and somata were analyzed. The analysis was separately conducted on mossy cells with soma located in the portions of the hilus that face the upper blade (upper hilus) and lower blade (lower hilus), respectively. The mossy cells in the upper hilus were found to be sexually dimorphic in both juvenile and peripubescent animals. At both ages females had a larger dendritic tree than males. This difference was due to a greater mean branch length and, in peripubescent animals, also to a greater number of branches. In juvenile males, the spines on the proximal dendrites (thorny excrescences) had a greater density than in females. No differences in spine density were present in peripubescent animals. Unlike the mossy cells in the upper hilus, the mossy cells in the lower hilus showed very few sex differences in juvenile animals and no differences in peripubescent animals. The few differences favored females, that had more proximal branches and a greater spine density on the distal dendrites than males. The results show that the mossy cells of the guinea-pig are sexually dimorphic prior to puberty. Extending a previous investigation, the present data provide evidence that sex differences are mainly confined to the dentate region corresponding to the upper blade and upper hilus. The observed segregation of the sexual dimorphism in the upper blade/upper hilus suggests that this region might underlie the sexual dimorphism in hippocampus-dependent memory functions.