Testosterone Reverses Ethanol-Induced Deficit in Spatial Reference Memory in Castrated Rats

Omega-3 fatty acids supplementation prevents learning and memory impairment induced by chronic ethanol consumption in adolescent male rats through restoration of inflammatory and oxidative responses

OBJECTIVE

Ethanol (Eth) intake is known to cause numerous detrimental effects on the structure and function of the brain, and it is commonly used as a psychostimulant drug by adolescents. Conversely, omega-3 (O3) can reduce the risk of cognitive decline and promote the maintenance of neurophysiological functions. In this study, we investigated the protective effects of O3 on behavioral alterations, oxidative stress, and interleukin-6 (IL-6) levels induced by chronic Eth intake during adolescence in rats.

MATERIALS AND METHODS

Adolescent male rats (21 days old) were divided as follows: (1) Vehicle, (2) Eth (Eth in drinking water [20%]), (3-5) Eth + O3 (50/100/150 mg/kg), and (6) O3 (150 mg/kg). After 5 weeks, Morris water maze (MWM) and passive avoidance (PA) tests were performed, and the hippocampal and cortical levels of oxidative stress markers and inflammatory indices were measured.

RESULTS

Adolescent Eth intake impairs learning and memory function in MWM and PA tests (groups × day, p < 0.05 and p < 0.001, respectively). It was shown that Eth induced oxidative stress and neuroinflammation. O3 improved learning and impairment induced by Eth by reducing the adverse effects of Eth on the oxidant/antioxidant balance in the hippocampi (for malondialdehyde [MDA]/thiol: p < 0.01, p < 0.001, respectively) and for superoxide dismutase (SOD)/catalase (CAT): p < 0.01 and p < 0.05, respectively). Furthermore, we found that O3 prevented the Eth-induced increase of hippocampal IL-6 (p < 0.001).

CONCLUSION

O3 supplementation acts as an effective approach to prevent learning and memory impairments induced by chronic Eth consumption during adolescence. In this respect, the antioxidant and anti-inflammatory properties of O3 seem to be the main underlying mechanisms of neuroprotection.

Conditioned preferences: Gated by experience, context, and endocrine systems

Central to the navigation of an ever-changing environment is the ability to form positive associations with places and conspecifics. The functions of location and social conditioned preferences are often studied independently, limiting our understanding of their interplay. Furthermore, a de-emphasis on natural functions of conditioned preferences has led to neurobiological interpretations separated from ecological context. By adopting a naturalistic and ethological perspective, we uncover complexities underlying the expression of conditioned preferences. Development of conditioned preferences is a combination of motivation, reward, associative learning, and context, including for social and spatial environments. Both social- and location-dependent reward-responsive behaviors and their conditioning rely on internal state-gating mechanisms that include neuroendocrine and hormone systems such as opioids, dopamine, testosterone, estradiol, and oxytocin. Such reinforced behavior emerges from mechanisms integrating past experience and current social and environmental conditions. Moreover, social context, environmental stimuli, and internal state gate and modulate motivation and learning via associative reward, shaping the conditioning process. We highlight research incorporating these concepts, focusing on the integration of social neuroendocrine mechanisms and behavioral conditioning. We explore three paradigms: 1) conditioned place preference, 2) conditioned social preference, and 3) social conditioned place preference. We highlight nonclassical species to emphasize the naturalistic applications of these conditioned preferences. To fully appreciate the complex integration of spatial and social information, future research must identify neural networks where endocrine systems exert influence on such behaviors. Such research promises to provide valuable insights into conditioned preferences within a broader naturalistic context.

Vitamin B12 administration prevents ethanol-induced learning and memory impairment through re-establishment of the brain oxidant/antioxidant balance, enhancement of BDNF and suppression of GFAP

There are growing evidence indicating that the adolescent brain is persistently affected by the use of psychostimulant agents. In this regard, alcohol drinking has become rather common among the adolescents in many societies during the last decade. It is currently well known that long-term ethanol exposure deteriorates various cognitive functions such as learning and memory. Mechanistically, these adverse effects have been shown to be mediated by oxidative damage to central nervous system. On the other hand, Vit-B12 is known to improve cognitive performance by suppression of oxidative parameters. Thus, in the present study we aimed to test whether treatment by Vit-B12 could prevent ethanol-induced complications in mice using behavioral and biochemical methods. Different groups of male Syrian mice received ethanol, ethanol+Vit-B12, Vit-B12 alone, or saline during adolescence and then learning and memory functions were assessed by Morris water maze (MWM) and Passive Avoidance (PA) tests. Finally, mice were sacrificed for measurement of biochemical factors. Results indicated that, adolescent ethanol intake impairs learning and memory function through exacerbation of oxidative stress and Vit-B12 treatment improves these complications by re-establishment of oxidant/anti-oxidant balance in CNS. Moreover, we found that Vit-B12 prevents ethanol-induced reduction of BDNF and enhancement of GFAP and acetylcholinesterase (AChE) activity. In conclusion, it seems that Vit-B12 supplementation could be used as an effective therapeutic strategy to prevent learning and memory defects induced by chronic alcohol intake during adolescence.

The Influence of Recreational Substance Use in TMS Research

(1) Background: Transcranial magnetic stimulation (TMS) approaches are widely used to study cortical and corticospinal function. However, responses to TMS are subject to significant intra-and inter-individual variability. Acute and chronic exposure to recreational substances alters the excitability of the sensorimotor system and may contribute to the variability in TMS outcome measures. The increasing prevalence of recreational substance use poses a significant challenge for executing TMS studies, but there is a lack of clarity regarding the influence of these substances on sensorimotor function. (2) Methods: The literature investigating the influence of alcohol, nicotine, caffeine and cannabis on TMS outcome measures of corticospinal, intracortical and interhemispheric excitability was reviewed. (3) Results: Both acute and chronic use of recreational substances modulates TMS measures of excitability. Despite the abundance of research in this field, we identify knowledge gaps that should be addressed in future studies to better understand the influence of these substances on TMS outcomes. (4) Conclusions: This review highlights the need for TMS studies to take into consideration the history of participant substance use and to control for acute substance use prior to testing.

Hormone levels in preterm and donor human milk before and after Holder pasteurization

BACKGROUND

After birth, breastfeeding is the exclusive source of hormonal signaling between mother and infant. Hospitalized infants often receive donor milk when their own mother's milk is unavailable.

METHODS

The presence of insulin, leptin, cortisol, progesterone, and testosterone was examined in samples from milk bank donors and mothers of preterm infants. We further investigated the effect of Holder pasteurization (HoP) on hormone levels.

RESULTS

Comparing nonpasteurized samples, leptin levels were nearly threefold higher in milk from mothers of preterm infants versus donated milk, and regardless of milk source, leptin levels were significantly decreased by HoP. Insulin concentrations were also decreased by HoP, and among mothers of preterm infants, obesity was associated with significantly higher content of leptin and insulin. While combined use of donor milk and HoP was associated with cortisol levels nearly threefold higher than those in nonpasteurized own mother's milk, progesterone and testosterone content did not differ by source or pasteurization.

CONCLUSIONS

The hormonal composition of breast milk is impacted by HoP and maternal obesity. Compared to nonpasteurized maternal milk, use of pasteurized donor milk dramatically decreases the intake of leptin while increasing the intake of cortisol. Further research is necessary to define optimal breast milk processing practices.

Androgen Affects the Dynamics of Intrinsic Plasticity of Pyramidal Neurons in the CA1 Hippocampal Subfield in Adolescent Male Rats

Androgen receptor (AR) is abundantly expressed in the preoptico-hypothalamic area, bed nucleus of stria terminalis, and medial amygdala of the brain where androgen plays an important role in regulating male sociosexual, emotional and aggressive behaviors. In addition to these brain regions, AR is also highly expressed in the hippocampus, suggesting that the hippocampus is another major target of androgenic modulation. It is known that androgen can modulate synaptic plasticity in the CA1 hippocampal subfield. However, to date, the effects of androgen on the intrinsic plasticity of hippocampal neurons have not been clearly elucidated. In this study, the effects of androgen on the expression of AR in the hippocampus and on the dynamics of intrinsic plasticity of CA1 pyramidal neurons were examined using immunohistochemistry, Western blotting and whole-cell current-clamp recording in unoperated, sham-operated, orchiectomized (OCX), OCX + testosterone (T) or OCX + dihydrotestosterone (DHT)-primed adolescent male rats. Orchiectomy significantly decreased AR-immunoreactivity, resting membrane potential, action potential numbers, afterhyperpolarization amplitude and membrane resistance, whereas it significantly increased action potential threshold and membrane capacitance. These effects were successfully reversed by treatment with either aromatizable androgen T or non-aromatizable androgen DHT. Furthermore, administration of the AR-antagonist flutamide in intact rats showed similar changes to those in OCX rats, suggesting that androgens affect the excitability of CA1 pyramidal neurons possibly by acting on the AR. Our current study potentially clarifies the role of androgen in enhancing the basal excitability of the CA1 pyramidal neurons, which may influence selective neuronal excitation/activation to modulate certain hippocampal functions.

Testosterone and Adult Neurogenesis

It is now well established that neurogenesis occurs throughout adulthood in select brain regions, but the functional significance of adult neurogenesis remains unclear. There is considerable evidence that steroid hormones modulate various stages of adult neurogenesis, and this review provides a focused summary of the effects of testosterone on adult neurogenesis. Initial evidence came from field studies with birds and wild rodent populations. Subsequent experiments with laboratory rodents have tested the effects of testosterone and its steroid metabolites upon adult neurogenesis, as well as the functional consequences of induced changes in neurogenesis. These experiments have provided clear evidence that testosterone increases adult neurogenesis within the dentate gyrus region of the hippocampus through an androgen-dependent pathway. Most evidence indicates that androgens selectively enhance the survival of newly generated neurons, while having little effect on cell proliferation. Whether this is a result of androgens acting directly on receptors of new neurons remains unclear, and indirect routes involving brain-derived neurotrophic factor (BDNF) and glucocorticoids may be involved. In vitro experiments suggest that testosterone has broad-ranging neuroprotective effects, which will be briefly reviewed. A better understanding of the effects of testosterone upon adult neurogenesis could shed light on neurological diseases that show sex differences.

Effects of testosterone dose on spatial memory among castrated adult male rats

Previous research on the activational effects of testosterone on spatial memory has produced mixed results, possibly because such effects are dose-dependent. We tested a wide range of testosterone doses using two spatial memory tasks: a working-reference memory version of the radial-arm maze (RAM) and an object location memory task (OLMT). Adult male Sprague-Dawley rats were castrated or sham-castrated and given daily injections of drug vehicle (Oil Sham and Oil GDX) or one of four doses of testosterone propionate (0.125, 0.250, 0.500, and 1.000 mg T) beginning seven days before the first day of behavioral tests and continuing throughout testing. For the RAM, four arms of the maze were consistently baited on each day of testing. Testosterone had a significant effect on working memory on the RAM, with the Oil Sham, 0.125 mg T, and 0.500 mg T groups performing better than the Oil GDX group. In contrast, there was no significant effect of testosterone on spatial reference memory on the RAM. For the OLMT, we tested long-term memory using a 2 h inter-trial interval between first exposure to two identical objects and re-exposure after one object had been moved. Only the 0.125 and 0.500 mg T groups showed a significant increase in exploration of the moved object during the testing trials, indicating better memory than all other groups. Testosterone replacement restored spatial memory among castrated male rats on both behavioral tasks, but there was a complex dose-response relationship; therefore, the therapeutic value of testosterone is likely sensitive to dose.

Effects of maternal stress during pregnancy on learning and memory via hippocampal BDNF, Arc (Arg3.1) expression in offspring

The intrauterine environment has a significant long-term impact on individual's life, this study was designed to investigate the effect of stress during pregnancy on offspring's learning and memory abilities and analyze its mechanisms from the expression of BDNF and Arc in the hippocampus of the offspring. A rat model of maternal chronic stress during pregnancy was mating from 3rd day during been subjecting to chronic unpredictable mild stress (CUMS). The body weights and behavioral changes were recorded, and plasma corticosterone levels were determined by radioimmunoassay. The learning and memory abilities of the offspring were measured by Morris water maze testing from PND 42. The expression of hippocampal BDNF and Arc mRNA and protein were respectively measured using RT-PCR and Western blotting. Results indicated that an elevation was observed in the plasma corticosterone level of rat model of maternal chronic stress during pregnancy, a reduction in the crossing and rearing movement times and the preference for sucrose. The body weight of maternal stress's offspring was lower than the control group, and the plasma corticosterone level was increased. Chronic stress during pregnancy had a significant impact on the spatial learning and memory of the offspring. The expression of BDNF mRNA and protein, Arc protein in offspring of maternal stress during pregnancy was attenuated and some relationships existed between these parameters. Collectively, these findings disclose that long-time maternal stress during pregnancy could destroy spatial learning and memory abilities of the offspring, the mechanism of which is related to been improving maternal plasma corticosterone and reduced hippocampal BDNF, Arc of offspring rats.

Gonadectomy reduces the density of androgen receptor-immunoreactive neurons in male rat's hippocampus: testosterone replacement compensates it

BACKGROUND

In the present study, the role of gonadectomy on memory impairment and the density of androgen receptor-immunoreactive neurons in rats' hippocampus as well as the ability of testosterone to compensate of memory and the density of androgen receptors in the hippocampus was evaluated.

METHODS

Adult male rats (except intact-no testosterone group) were bilaterally castrated, and behavioral tests performed 2 weeks later. Animals bilaterally cannulated into lateral ventricles and then received testosterone (10, 40 and 120 µg/0.5 µl DMSO) or vehicle (DMSO; 0.5 µl) for gonadectomized-vehicle group, 30 min before training in water maze test. The androgen receptor-immunoreactive neurons were detected by immunohistochemical technique in the hippocampal areas.

RESULTS

In the gonadectomized male rats, a memory deficit was found in Morris water maze test on test day (5th day) after DMSO administration. Gonadectomy decreased density of androgen receptor-immunoreactive neurons in the rats' hippocampus. The treatment with testosterone daily for 5 days attenuated memory deficits induced by gonadectomy. Testosterone also significantly increased the density of androgen receptor-immunoreactive neurons in the hippocampal areas. The intermediate dose of this hormone (40 µg) appeared to have a significant effect on spatial memory and the density of androgen receptor-immunoreactive neurons in gonadectomized rats' hippocampus.

CONCLUSIONS

The present study suggests that testosterone can compensate memory failure in gonadectomized rats. Also testosterone replacement can compensate the reduction of androgen receptor-immunoreactive neurons density in the rats' hippocampus after gonadectomy.

Protective effect of berberine, an isoquinoline alkaloid ameliorates ethanol-induced oxidative stress and memory dysfunction in rats

Memory impairment induced by ethanol in rats is a consequence of changes in the CNS that are secondary to impaired oxidative stress and cholinergic dysfunction. Treatment with antioxidants and cholinergic agonists are reported to produce beneficial effects in this model. Berberine, an isoquinoline alkaloid is reported to exhibit antioxidant effect and cholinesterase (ChE) inhibitor activity. However, no report is available on the influence of berberine on ethanol-induced memory impairment. Therefore, we tested its influence against cognitive dysfunction in ethanol-induced rats using Morris water maze paradigm. Lipid peroxidation and glutathione levels as parameter of oxidative stress and cholinesterase (ChE) activity as a marker of cholinergic function were assessed in the cerebral cortex and hippocampus. Forty five days after ethanol treated rats showed a severe deficit in learning and memory associated with increased lipid peroxidation, decreased glutathione, and elevated ChE activity. In contrast, chronic treatment with berberine (25-100mg/kg, p.o., once a day for 45days) improved cognitive performance, and lowered oxidative stress and ChE activity in ethanol treated rats. In another set of experiments, berberine (100mg/kg) treatment during training trials also improved learning and memory, and lowered oxidative stress and ChE activity. Chronic treatment (45days) with vitamin C, and donepezil during training trials also improved ethanol-induced memory impairment and reduced oxidative stress and/or cholinesterase activity. In conclusion, the present study demonstrates that treatment with berberine prevents the changes in oxidative stress and ChE activity, and consequently memory impairment in ethanol treated rats.

Tiliacora triandra, an Anti-Intoxication Plant, Improves Memory Impairment, Neurodegeneration, Cholinergic Function, and Oxidative Stress in Hippocampus of Ethanol Dependence Rats

Oxidative stress plays an important role in brain dysfunctions induced by alcohol. Since less therapeutic agent against cognitive deficit and brain damage induced by chronic alcohol consumption is less available, we aimed to assess the effect of Tiliacora triandra extract, a plant possessing antioxidant activity, on memory impairment, neuron density, cholinergic function, and oxidative stress in hippocampus of alcoholic rats. Male Wistar rats were induced ethanol dependence condition by semivoluntary intake of alcohol for 15 weeks. Alcoholic rats were orally given T. triandra at doses of 100, 200, and 400 mg·kg⁻¹BW for 14 days. Memory assessment was performed every 7 days while neuron density, activities of AChE, SOD, CAT, and GSH-Px and, MDA level in hippocampus were assessed at the end of study. Interestingly, the extract mitigated the increased escape latency, AChE and MDA level. The extract also mitigated the decreased retention time, SOD, CAT, and GSH-Px activities, and neurons density in hippocampus induced by alcohol. These data suggested that the extract improved memory deficit in alcoholic rats partly via the decreased oxidative stress and the suppression of AChE. Therefore, T. triandra is the potential reagent for treating brain dysfunction induced by alcohol. However, further researches are necessary to understand the detail mechanism and possible active ingredient.

On the effects of testosterone on brain behavioral functions

Testosterone influences the brain via organizational and activational effects. Numerous relevant studies on rodents and a few on humans focusing on specific behavioral and cognitive parameters have been published. The results are, unfortunately, controversial and puzzling. Dosing, timing, even the application route seem to considerably affect the outcomes. In addition, the methods used for the assessment of psychometric parameters are a bit less than ideal regarding their validity and reproducibility. Metabolism of testosterone contributes to the complexity of its actions. Reduction to dihydrotestosterone by 5-alpha reductase increases the androgen activity; conversion to estradiol by aromatase converts the androgen to estrogen activity. Recently, the non-genomic effects of testosterone on behavior bypassing the nuclear receptors have attracted the interest of researchers. This review tries to summarize the current understanding of the complexity of the effects of testosterone on brain with special focus on their role in the known sex differences.

Androgen Modulation of Hippocampal Structure and Function

Androgens have profound effects on hippocampal structure and function, including induction of spines and spine synapses on the dendrites of CA1 pyramidal neurons, as well as alterations in long-term synaptic plasticity (LTP) and hippocampally dependent cognitive behaviors. How these effects occur remains largely unknown. Emerging evidence, however, suggests that one of the key elements in the response mechanism may be modulation of brain-derived neurotrophic factor (BDNF) in the mossy fiber (MF) system. In male rats, orchidectomy increases synaptic transmission and excitability in the MF pathway. Testosterone reverses these effects, suggesting that testosterone exerts tonic suppression on MF BDNF levels. These findings suggest that changes in hippocampal function resulting from declining androgen levels may reflect the outcome of responses mediated through normally balanced, but opposing, mechanisms: loss of androgen effects on the hippocampal circuitry may be compensated, at least in part, by an increase in BDNF-dependent MF plasticity.

Assessment of the effects of sex and sex hormones on spatial cognition in adult rats using the Barnes maze

Although sex differences and hormone effects on spatial cognition are observed in humans and animals, consensus has not been reached regarding exact impact on spatial working or reference memory. Recent studies in rats suggest that stress and/or reward, which are often different in tasks used to assess spatial cognition, can contribute to the inconsistencies in the literature. To minimize the impact of these sex- and sex hormone-sensitive factors, we used the Barnes maze to compare spatial working memory, spatial reference memory and spatial learning strategy in adult male, female, gonadectomized (GDX) male, and GDX male rats supplemented with 17β-estradiol (E) or testosterone propionate (TP). Rats received four acquisition trials, four trials 24h later, and a single retention trial one week after. Males and females acquired the task during the first four trials and retained the task thereafter. In contrast, GDX rats took longer to acquire the task and showed retention deficits at 1week. All deficits were attenuated similarly by TP and E. Assessment of search patterns also showed that strategies in the males transitioned from random to spatially focused and eventually direct approaches to the goal. However, this transition was faster in control and GDX-TP than in GDX and GDX-E rats. In contrast, the females almost invariantly followed the maze edge in thigmotactic, serial searches. Thus, while Barnes maze reveals activational, in part estrogenic effects on spatial cognition in males, its amenability to animals' use of multiple strategies may limit its ability to resolve mnemonic differences across sex.

Testosterone influences spatial strategy preferences among adult male rats

Males outperform females on some spatial tasks, and this may be partially due to the effects of sex steroids on spatial strategy preferences. Previous work with rodents indicates that low estradiol levels bias females toward a striatum-dependent response strategy, whereas high estradiol levels bias them toward a hippocampus-dependent place strategy. We tested whether testosterone influenced the strategy preferences in male rats. All subjects were castrated and assigned to one of three daily injection doses of testosterone (0.125, 0.250, or 0.500 mg/rat) or a control group that received daily injections of the drug vehicle. Three different maze protocols were used to determine rats' strategy preferences. A low dose of testosterone (0.125 mg) biased males toward a motor-response strategy on a T-maze task. In a water maze task in which the platform itself could be used intermittently as a visual cue, a low testosterone dose (0.125 mg) caused a significant increase in the use of a cued-response strategy relative to control males. Results from this second experiment also indicated that males receiving a high dose of testosterone (0.500 mg) were biased toward a place strategy. A third experiment indicated that testosterone dose did not have a strong influence on the ability of rats to use a nearby visual cue (floating ball) in the water maze. For this experiment, all groups seemed to use a combination of place and cued-response strategies. Overall, the results indicate that the effects of testosterone on spatial strategy preference are dose dependent and task dependent.

Testosterone modulates spatial recognition memory in male rats

A growing body of research indicates that testosterone influences spatial cognition in male rats; however, the overwhelming majority of studies have been conducted on tasks motivated by either food deprivation or water escape. The hippocampus-dependent version of the Y-maze task, which characterizes spatial recognition memory, capitalizes on the propensity of rats to gravitate toward novel spatial environments and is not contingent upon either appetite or the stress associated with water escape, two factors also affected by testosterone. Accordingly, the aim of the current study was to examine the effects of orchidectomy and subsequent testosterone treatment on spatial recognition memory. Orchidectomy did not impact spatial recognition memory when the delay between the information and retention trials of the Y-maze task was 24h. Alternatively, on the second Y-maze task, which featured a 48-h delay between trials, orchidectomy reduced, and treatments that produced higher levels of testosterone restored, preference for the arm associated with the novel spatial environment. Importantly, there were no differences in activity levels as a function of orchidectomy or testosterone treatment on either of the two tasks. Consistent with previous findings, orchidectomy attenuated, and testosterone treatment restored, both body weight gain and the relative weight of the androgen-sensitive ischiocavernosus muscle, which confirmed the efficacy of orchidectomy and testosterone treatments on physiological outcomes. Therefore, testosterone influenced spatial cognition on a task that minimized the influence of non-mnemonic factors and took advantage of the innate preference of rodents to seek out novel spatial environments.

Resveratrol abrogates alcohol-induced cognitive deficits by attenuating oxidative-nitrosative stress and inflammatory cascade in the adult rat brain

Chronic alcohol intake is known to induce permanent cognitive deficits along with enhanced oxidative-nitrosative stress and activation of neuroinflammatory cascade. In the present study, we investigated the protective effect of resveratrol, a natural polyphenolic phytoalexin against chronic alcohol-induced cognitive dysfunction and neuroiflammatory cascade in the brain of adult rats chronically administered ethanol. Male Wistar rats were adminstered ethanol (10g/kg; oral gavage) for ten weeks and treated with resveratrol (5, 10 and 20mg/kg) for the same duration. Ethanol-exposed rats showed impaired spatial navigation in the Morris water maze test and poor retention in the elevated plus maze task which was coupled with enhanced acetylcholinesterase activity, increased oxidative-nitrosative stress, cytokines (TNF-alpha and IL-1beta), NF-kappa β and caspase-3 levels in different brain regions (cerebral cortex and hippocampus) of ethanol-treated rats. Co-administration with resveratrol significantly and dose-dependently prevented all the behavioral, biochemical and molecular deficits. Correlatively, the results of the present study revealed that treatment with resveratrol significantly prevented cognitive deficits induced by chronic ethanol exposure not only by modulating oxido-nitrosative stress but also by attenuating the enhanced levels of pro-inflammatory cytokines (TNF-α and IL-1β), NF-kβ and caspase-3 in different brain regions of ethanol treated rats. Therefore, mechanism underlying the neuroprotective effects of resveratrol observed in our study may be due to its antioxidant, anti-inflammatory and neuromodulating activities.

Interactions between opioids and anabolic androgenic steroids: implications for the development of addictive behavior

Over the past decades, research on doping agents, such as anabolic androgenic steroids (AAS), has revealed that these compounds are often used in combination with other drugs of abuse. It seems that misuse of AAS probably involves more than a desire to enhance appearance or sports performance and studies have revealed that steroids are commonly connected with alcohol, opioids, tobacco, and psychotropic drugs. We have observed that AAS may interact with the endogenous opioids, excitatory amino acids, and dopaminergic pathways involved in the brain reward system. Furthermore, our studies provide evidence that AAS may induce an imbalance in these signal systems leading to an increased sensitivity toward opioid narcotics and central stimulants. In fact, studies performed in various clinics have shown that individuals taking AAS are likely to get addicted to opioids like heroin. This chapter reviews current knowledge on interactions between AAS and endogenous as well as exogenous opioids based not only on research in our laboratory but also on research carried out by several other clinical and preclinical investigators.

Dose-response effect of black maca (Lepidium meyenii) in mice with memory impairment induced by ethanol

Previous studies have shown that black variety of maca has beneficial effects on learning and memory in experimental animal models. The present study aimed to determine whether the hydroalcoholic extract of black maca (BM) showed a dose-response effect in mice treated with ethanol 20% (EtOH) as a model of memory impairment. Mice were divided in the following groups: control, EtOH, ascorbic acid (AA) and 0.125, 0.25, 0.50 and 1.00 g/kg of BM plus EtOH. All treatments were orally administered for 28 days. Open field test was performed to determine locomotor activity and water Morris maze was done to determine spatial memory. Also, total polyphenol content in the hydroalcoholic extract of BM was determined (0.65 g pyrogallol/100 g). Mice treated with EtOH took more time to find the hidden platform than control during escape acquisition trials; meanwhile, AA and BM reversed the effect of EtOH. In addition, AA and BM ameliorated the deleterious effect of EtOH during the probe trial. Correlation analyses showed that the effect of BM a dose-dependent behavior. Finally, BM improved experimental memory impairment induced by ethanol in a dose-response manner due, in part, to its content of polyphenolic compounds.

Effects of testosterone on spatial learning and memory in adult male rats

A male advantage over females for spatial tasks has been well documented in both humans and rodents, but it remains unclear how the activational effects of testosterone influence spatial ability in males. In a series of experiments, we tested how injections of testosterone influenced the spatial working and reference memory of castrated male rats. In the eight-arm radial maze, testosterone injections (0.500 mg/rat) reduced the number of working memory errors during the early blocks of testing but had no effect on the number of reference memory errors relative to the castrated control group. In a reference memory version of the Morris water maze, injections of a wide range of testosterone doses (0.0625-1.000 mg/rat) reduced path lengths to the hidden platform, indicative of improved spatial learning. This improved learning was independent of testosterone dose, with all treatment groups showing better performance than the castrated control males. Furthermore, this effect was only observed when rats were given testosterone injections starting 7 days prior to water maze testing and not when injections were given only on the testing days. We also observed that certain doses of testosterone (0.250 and 1.000 mg/rat) increased perseverative behavior in a reversal-learning task. Finally, testosterone did not have a clear effect on spatial working memory in the Morris water maze, although intermediate doses seemed to optimize performance. Overall, the results indicate that testosterone can have positive activational effects on spatial learning and memory, but the duration of testosterone replacement and the nature of the spatial task modify these effects.

Alcohol breaks down interhemispheric inhibition in females but not in males: alcohol and frontal connectivity

INTRODUCTION

Alcohol has renowned behavioral disinhibitory properties which are suggested to involve reductions in frontal lobe functioning as a result of diminished interhemispheric connectivity.

METHODS

To examine sex differences in frontal interhemispheric connectivity in response to alcohol, 12 female and ten male healthy volunteers received a single administration of 0.5 per thousand alcohol in a placebo-controlled counterbalanced crossover design. Paired-pulse transcranial magnetic stimulation was applied to measure transcallosal inhibition (TCI) between the left and right primary motor cortex (M1).

RESULTS

Results showed significant reductions in TCI after alcohol administration in female participants exclusively.

DISCUSSION

These findings provide the first evidence that moderate doses of alcohol differentially affect frontal interhemispheric connectivity in males and females. The present data may shed new light on the physiological mechanisms underlying sex differences in the susceptibility to alcohol.

Suppression of neuro-inflammatory signaling cascade by tocotrienol can prevent chronic alcohol-induced cognitive dysfunction in rats

Chronic alcohol intake is known to induce the selective neuronal damage associated with increase oxidative-nitrosative stress and activation of inflammatory cascade finally resulting in neuronal apoptosis and thus dementia. In the present study, we investigated the comparative effect of both the isoforms of vitamin E, alpha-tocopherol and tocotrienol against chronic alcohol-induced cognitive dysfunction in rats. Male Wistar rats were given ethanol (10g/kg; oral gavage) for 10 weeks, and treated with alpha-tocopherol and tocotrienol for the same duration. The learning and memory behavior was assessed using Morris water maze and elevated plus maze test. The rats were sacrificed at the end of 10th week and cytoplasmic fractions of cerebral cortex and hippocampus were prepared for the quantification of acetylcholinesterase activity, oxidative-nitrosative stress parameters, tumor necrosis factor-alpha (TNF-alpha), and interleukin-1beta (IL-1beta). From the 6th week onwards, ethanol-treated rats showed significant increase in transfer latency in both the behavioral paradigms which was coupled with enhanced acetylcholinesterase activity, increased oxidative-nitrosative stress, TNF-alpha and IL-1beta levels in different brain regions of ethanol-treated rats. Co-administration of alpha-tocopherol as well as tocotrienol significantly and dose-dependently prevented these behavioral, biochemical and molecular changes in the brains of ethanol-treated rats. However, the effects were more pronounced with tocotrienol. The current study thus demonstrates the possible involvement of oxidative-nitrosative stress mediated activation of inflammatory cascade in chronic alcohol-induced cognitive dysfunction and also suggests the effectiveness of vitamin E isoforms, of which tocotrienol being more potent, in preventing the cognitive deficits associated with chronic alcohol consumption.

Castration differentially affects spatial working and reference memory in male rats

A male advantage for spatial learning and memory tasks is well documented among humans and rodents. A possible physiological cause for this male advantage is activational effects of androgens among males. The spatial memory of eight castrated and eight sham-castrated adult male rats was compared using a working-reference memory version of the eight-arm radial arm maze followed by a reference memory version of the Morris water maze. After maze testing, blood was collected from each rat, and testosterone levels were determined using radioimmunoassay. In the radial arm maze, castrates committed significantly more working memory errors and significantly fewer reference memory errors than did shams. In the water maze, no statistically significant differences were found for acquisition or retention. There was a trend for shams with higher testosterone levels to have better retention in the water maze, but this seemed to be due to higher levels of perseverance rather than better reference memory. Castration may have affected performance in the radial arm maze and not in the water maze because the radial arm maze was a more difficult task or because the water maze was aversively motivated while the radial arm maze was appetitively motivated. Our results indicate that androgens improve working memory and may impair reference memory, but the effects of androgens on reference memory seem to be task dependent.

Endogenous opiates and behavior: 2005

This paper is the 28th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2005 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity, neurophysiology and transmitter release (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); immunological responses (Section 17).