Participation of Glutamatergic Ionotropic Receptors in Excitotoxicity: The Neuroprotective Role of Prolactin.

Glutamate (Glu) is known as the main excitatory neurotransmitter in the central nervous system. It can trigger a series of processes ranging from synaptic plasticity to neurophysiological regulation. To carry out its functions, Glu acts via interaction with its cognate receptors, which are ligand-dependent. Glutamatergic receptors include ionotropic and metabotropic categories. The first allows the passage of ions through the postsynaptic membrane, while the metabotropic subtype activates signaling cascades through second messengers. It is well known that an excess of extracellular Glu concentration induces overstimulation of ionotropic glutamatergic receptors (iGluRs), causing the excitotoxicity phenomenon that leads to neuronal damage and cell death. Excitotoxicity plays a crucial role in different brain pathologies such as brain strokes, epilepsy and neurodegenerative disorders. However, until now, there are no effective neuroprotective compounds to prevent or rescue neurons from excitotoxicity. Thus, the continuous elucidation of the molecular mechanisms underlying excitotoxicity in order to prevent damage or neuronal death is necessary. Therefore, the aim of this review was to summarize the current knowledge regarding iGluRs, while describing their structures and molecular mechanisms of action, including their role in excitotoxicity, as well as the current strategies to reduce excitotoxic damage. Particularly, strategies mediated by prolactin, a somatotropin family-related hormone that displays a significant neuroprotective effect against both Glu and kainic acid-induced excitotoxicity in the hippocampus, are described. Finally, the role of prolactin as a possible molecule in the treatment of excitotoxicity in neurological diseases is discussed.

Prolactin prevents the kainic acid-induced neuronal loss in the rat hippocampus by inducing prolactin receptor and putatively increasing the VGLUT1 overexpression.

Neuroprotective effects of short prolactin (PRL) pre-treatment against kainic acid (KA)-induced damage include neuron loss avoidance in all hippocampal regions and attenuation of seizures. Recent evidence points PRL receptor (PRL-R) as mediator of such neuroprotective effects and seizures as regulators of neuronal marker transcript expression in the hippocampus. Here, we investigated if a daily PRL dose of 100 µg or vehicle for 14 days in ovariectomized rats (OVX) prevents neuron loss induced by KA administered on the third day of PRL treatment in a systemic single dose of 7.5 mg/kg or vehicle, and promotes PRL-R, vesicular glutamate transporter 1 (VGLUT1) and glutamic acid decarboxylase 65 (GAD65) expression changes in the hippocampus of sacrificed rats 27 days after the KA administration. Immunostaining for Neu-N and PRL-R revealed significant neuron number and PRL-R expression reduction induced by KA that was prevented and turned into overexpression respectively in all hippocampal regions when PRL was added; while VGLUT1,and GAD65 immunostaining displayed expression decrease in the CA1 of injured rats, prevented in the last case and turned into VGLUT1, overexpression when administered PRL. These data indicate that chronic PRL administration before damage induces hippocampal neuroprotection associated with PRL-R and VGLUT1 overexpression, the latter in a regiondependent way.

The Philippines health system review

The Asia Pacific Observatory on Health Systems and Policies (the APO) is a collaborative partnership of interested governments, international agencies, foundations, and researchers that promotes evidence-informed health systems policy regionally and in all countries in the Asia Pacific region. The APO collaboratively identifies priority health system issues across the Asia Pacific region; develops and synthesizes relevant research to support and inform countries' evidence-based policy development; and builds country and regional health systems research and evidence-informed policy capacity.

Supplementation with Lactobacillus rhamnosus SP1 normalises skin expression of genes implicated in insulin signalling and improves adult acne.

Systemic supplementation with probiotics is increasingly being explored as a potential treatment strategy for skin disorders. Because both the gut-skin axis and dysregulation of insulin signalling have been implicated in the pathogenesis of adult acne, we designed the current study to evaluate the effect of supplementation with the probiotic strain Lactobacillus rhamnosus SP1 (LSP1) on skin expression of genes involved in insulin signalling and acne improvement in adult subjects. A pilot, randomised, double-blinded, placebo-controlled study was conducted with 20 adult subjects (14 females and 6 males; mean age: 33.7±3.3 years) with acne. Over a 12-week period, the probiotic group (n=10) consumed a liquid supplement containing LSP1 at a dose of 3×109 cfu/day (75 mg/day), whereas the placebo group (n=10) received a liquid lacking probiotics. Paired skin biopsies - one obtained before treatment initiation and one obtained at the end of the 12-week treatment period - were analysed for insulin-like growth factor 1 (IGF1) and forkhead box protein O1 (FOXO1) gene expression. The clinical criterion for efficacy was the investigator's global improvement rating on a five-point scale. Compared with baseline, the probiotic group showed a 32% (P<0.001) reduction, as well as a 65% increase (P<0.001) in IGF1 and FOXO1 gene expression in the skin, respectively. No such differences were observed in the placebo group. Patients in the probiotic group had an adjusted odds ratio of 28.4 (95% confidence interval = 2.2-411.1, P<0.05) to be rated by physicians as improved/markedly improved (versus worsened or unchanged) compared with the placebo group. We conclude that supplementation with the probiotic strain LSP1 normalises skin expression of genes involved in insulin signalling and improves the appearance of adult acne.

Ovariectomy increases the age-induced hyperphosphorylation of Tau at hippocampal CA1.

One of the main hallmarks of Alzheimer's disease includes the neurofibrillary tangles formation produced by hyperphosphorylation of the Tau protein, whose expression is putatively regulated by the ovarian hormones estradiol and progesterone. Hippocampus is a brain region that participates in many functions related to learning and memory; in addition, it is abundant in both estradiol and progesterone receptors. In this study, we explore the expression of Tau hyperphosphorylation at hippocampus and the performance of rats in an autoshaping learning task at 5, 10 and 15 months after the ovaries removal. In these animals, ovariectomy was performed at 3 months of age. These data were compared with those derived from intact rats at 8, 13 and 18 months old. A clear decrease in the number of conditioned responses of both intact and ovariectomized rats in the autoshaping learning task was observed. The interaction of both factors confirms that, in this test, learning varies depending on aging and the presence or absence of ovaries. A progressive increase in hippocampal Tau phosphorylation at Ser-396 was observed in either intact or ovariectomized rats. Interestingly, an interaction between the analyzed factors shows that such hyperphosphorylation was potentiated by the absence of ovaries. These results emphasize the importance of aging and the lack of ovarian hormones for an associative learning test and for the expression of one of the most important hallmarks of Alzheimer's disease.

An enriched environment and 17-beta estradiol produce similar pro-cognitive effects on ovariectomized rats.

Estrogen depletion due to aging, surgery or pathological events can cause a multitude of problems, including neurodegenerative alterations. In rodents without ovaries, 17-beta estradiol (E2) has been shown to produce beneficial effects on cognition, stimulating brain regions (e.g., the neocortex, hippocampus and amygdala) related to cognition and learning. Another treatment that stimulates these brain regions is an enriched environment (EE), which is a complex set of external factors in the immediate surroundings that facilitates greater stimulation of sensorial, cognitive and motor circuits of the brain. The aim of the present study was to test, using an animal model of ovariectomy-induced impairment of memory, the relative effect of E2 (with a time-released pellet; 1 µg/rat/day), EE exposure and a combination of both treatments. Experimental and control groups were submitted to two memory tests 18 weeks post-surgery: the autoshaping learning task (ALT) for measuring associative learning and the novel object recognition test (NORT) for evaluating short- and long-term memory. To assess potential motor impairments caused by treatments, all rats were tested after the ALT in an automatic activity counter. Results from ALT show that the ovariectomy blocked the conditioned responses displayed, an effect rescued by chronic treatment with estrogen or EE exposure. The combination of both treatments did not improve the results obtained separately. In the NORT, the exploration time for recognizing a novel object was similar in the short run with all groups, but greater in the long run with hormone administration or EE exposure. As with the ALT, in the NORT there was no improvement shown by the combination treatment. These data were not masked by changes in spontaneous activity because this parameter was not modified in the rats by either treatment. Possible action mechanisms are proposed, taking into account the role of corticosterone and BDNF on cognition.

Anxiolytic-like effects of a new 1-N substituted analog of melatonin in pinealectomized rats.

In spite of the wide variety of drugs available for treating anxiety, this disorder continues to represent a worldwide health problem that is classified within the first 10 causes of disability. Therefore, the search continues for new antianxiety agents, particularly those not related to benzodiazepines. Even though melatonin has been prescribed as an anxiolytic drug, its use is currently limited due to its short half-life and photo-sensitivity, among other disadvantages. The present study explores the antianxiety properties of a new 1-N substituted melatonin analog, M3C, in pinealectomized rats submitted to two behavioral tests (the cumulative burying behavior paradigm and the elevated plus-maze). Results from both tests show that M3C is effective as an anxiolytic-like agent, at doses lower than any other melatonin analog previously reported. The blocking of these actions by luzindole together with the available data suggests that the anxiolytic properties of M3C are mediated by MT1 and MT2 receptors.

Role of estrogens on some cognition-related aspects.

Two of the most studied brain areas related with learning and memory are prefrontal cortex and hippocampus. However, serious inconsistencies arise when these regions are analyzed in relation to the role of estrogens on cognitive deterioration. Some of these contradictions are reviewed in the context of the recently proposed critical period hypothesis, which takes into account the frame-time after cessation of ovarian function. Other factors related with cognition and influenced by estrogens include their role on; a) cholinergic central transmission, b) spinogenesis and synaptogenesis at hippocampus, and c) classical genomic and rapid non genomic effects. Understanding the cellular and molecular basis of these phenomena is vital for designing novel therapeutic actions applicable to human health and disease.

Effect of a M1 allosteric modulator on scopolamine-induced amnesia.

It is well accepted that acetylcholine is involved in memory and learning processes and that loss of memory is characteristic of Alzheimer's disease (AD). Several muscarinic agonists have been shown to be clinically effective in the treatment of AD. However, their use has been limited due to adverse side effects. As a result, more selective M1 agonists are expected to be the next generation of agents for the treatment of AD. One pharmacological approach to evaluate possible cognitive effects of compounds includes their ability to reverse scopolamine-induced amnesia. In the current study the succinamide and succinimide of p-aminophenol, two newly synthesized compounds that were previously designed to be acetylcholine analogues, were evaluated in a Pavlovian/Instrumental autoshaped memory task. Simultaneously, docking studies on the M1 receptor were done. The scopolamine-induced amnesia was reversed by the amide but not the imide. These findings are in line with results derived from the docking simulations, and suggest that at least the succinamide of p-aminophenol could represent a novel candidate for the treatment of AD.

Influence of forced swimming-induced stress on the anxiolytic-like effect of 5HT(1A) agents in mice.

RATIONALE: Stress has been related to both anxiety and mood disorders. Forced swimming (FS) is a type of stress that is able to modify the activity of serotonin (5-HT) and GABA in the central nervous system. 5-HT(1A) compounds have been shown to be anxiolytic in a variety of behavioral models and in clinical studies. OBJECTIVE: The main purpose of the present study was to analyze the effect of FS on the anxiolytic-like actions of three 5-HT(1A) compounds. METHODS: Stressed (ST) and unstressed (UST) mice were evaluated in the exploratory behavior test (EBT) or burying behavior test (BBT). In addition, the action of increasing doses of the 5-HT(1A) compounds buspirone, 8-OH-DPAT and indorenate in ST and UST mice was analyzed using the EBT. A spontaneous ambulatory behavior test was carried out immediately after the anxiety tests. RESULTS: One session of FS induced anxiolytic-like behavior in mice tested in both the EBT and the BBT. This effect of FS was blocked by a previous administration of either picrotoxin or WAY 100635. The 5-HT(1A) compounds produced a clear anxiolytic-like effect in UST animals. By contrast, with low doses of either 8-OH-DPAT (0.01 mg/kg), buspirone (0.03 mg/kg) or indorenate (0.3, 0.6 mg/kg) ST mice showed a decrease in the anti-anxiety-like effect observed after FS. No change in ambulation that could mask the results of the anxiety test was registered. CONCLUSIONS: The present data provide evidence that FS induces changes in the effect of 5-HT(1A) agents. The participation of the 5-HT and/or GABA systems in these stress-induced effects is discussed.

Diazepam, but not buspirone, induces similar anxiolytic-like actions in lactating and ovariectomized Wistar rats.

Previous reports indicate that the behavioural effects (including anxiolytic-like actions, hypothermia, "serotonergic syndrome," maternal behaviour and aggression and reduction in ambulation) of the 5-HT1A agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), are completely blocked in lactating rats. The present study compares the behavioural effects of buspirone (1.25, 2.5 and 5.0 mg/kg) and diazepam (0.5, 1.0, 2.0 and 4.0 mg/kg) between ovariectomized and mid-lactating rats. The study was carried out on Wistar female rats under inverted light/dark cycle conditions, by using the burying behaviour paradigm, the elevated plus maze and a general activity test. In both ovariectomized and lactating rats, diazepam produced a dose-dependent reduction in burying behaviour and an increase in the time spent in open arms, responses interpreted as anxiolytic. Buspirone at all doses (1.25, 2.5 and 5.0 mg/kg) produced clear motor impairments in lactating, but not in ovariectomized animals, indicating that the effects of this drug on the anxiety paradigms are unspecific. Diazepam, by contrast, at the highest dose (4.0 mg/kg) similarly inhibited ambulation in both conditions. In the elevated plus maze, control lactating subjects spent more time in the open arms compared with saline-treated ovariectomized subjects, suggesting an anxiolytic-like effect of lactation per se. The present results support the idea that some behavioural actions of drugs acting at the serotonergic system vary between ovariectomized and lactating rats.

Effect of red peppers (Capsicum frutescens) intake during gestation on thermonociceptive response of rat offspring.

Oral administration of aqueous red pepper (Capsicum frutescens, Cf) solution and low capsaicin (8-methyl-N-vanillyl-6-nonenamide) doses during gestation produces an increase in the latency of the thermonociceptive escape response of rat offspring. The present work shows that different amounts of Cf (10%, 25% and 50%) incorporated to normal food of gestating rats modify in a dose-dependent manner the flexion reflex latency (R), as well as the latency of appearance of antialgesic behaviours expressed as paw lick (P) and escape response (E) using the hot plate test (53 degrees C+/-0.5 degrees C). The latency of the same parameters was tested in the same subjects 55 days later to determine the persistence of this effect. Results show an increase in latency of the three parameters R, P and E in all experimental groups with respect to controls. Animals (Cf, 25% group) tested 55 days after the first test exhibited latencies similar to controls, which suggests that the process is reversible.

The differential effect of the anxiolytic agent 8-OH-DPAT during lactation is independent of pup withdrawal and maternal behavior.

Injection of the serotonergic agonist, 8-hydroxy-2-(di-n-propylamino-tetralin (8-OH-DPAT) (0.5 mg/kg ip) produced a clear anxiolytic-like effect (as measured in the burying behavior test), after parturition, which remains until day 6 of lactation. Thereafter 8-OH-DPAT completely lacked action. In order to analyze whether lactation prevented the action of 8-OH-DPAT, dams were separated from their pups for five consecutive days. The blockade of the anxiolytic effect of 8-OH-DPAT does not disappear by isolation of the mothers from their offspring or from neighboring pups. Finally, to investigate the possible role of maternal behavior in the blockade of the anxiolytic effect of 8-OH-DPAT a third experiment was made in which ovariectomized females were rendered maternal by the sensitization procedure. These females respond normally to the antianxiety actions of 8-OH-DPAT. Results suggest that a long-term clue triggered by lactation, possibly related to prolactin secretion, interferes with the anxiolytic effect of 8-OH-DPAT.

Inhibitory effect of buspirone and diazepam, but not of 8-OH-DPAT, on maternal behavior and aggression.

The action of diazepam (0.0, 1.0, and 2.0 mg/kg) and the serotonergic compounds buspirone (0.0, 2.5, and 5.0 mg/kg) and 8-OH-DPAT (0.0, 0.1, and 1.0 mg/kg) on maternal behavior and aggression were studied. An activity test was made after these treatments to control for unspecific actions due to motor impairment. Diazepam and buspirone dose-dependently inhibited the expression of maternal aggression and the active components of maternal behavior such as retrieving and nest building. 8-OH-DPAT did not affect these behaviors. 8-OH-DPAT (1.0 mg/kg) provoked the serotonergic syndrome and hypothermia; however, ovariectomized animals showed more signs of the syndrome and a decrease in body temperature after 8-OH-DPAT than lactating rats. Buspirone, but not the other anxiolytics, reduced motor activity. The role of drugs acting at the serotonergic, dopaminergic, and GABA-benzodiazepine systems in the control of maternal behavior and aggression is discussed.

Sexual differentiation modifies the allopregnanolone anxiolytic actions in rats.

The administration of progesterone (0.0, 1.0 and 2.0 mg/rat, s.c.) and allopregnanolone (5 alpha, 3 alpha dihydroprogesterone) (0.0, 0.5 and 1.0 mg/rat, s.c.) to both, males and females, produced a similar reduction in burying behavior. Only allopregnanolone showed a gender-dependent effect on burying behavior latency. Allopregnanolone actions were established in five groups of animals according to their neonatal hormonal manipulation: intact males and females, neonatally-testosterone propionate-treated female rats (TP, 30 and 120 micrograms/rat, s.c. at day 5) and neonatally (4-12 h after delivery) castrated males. Males and females showed a reduction in anxiety after treatment with allopregnanolone. Both neonatally-androgenized-females and -castrated males were completely insensitive to allopregnanolone anxiolytic action tested in both burying behavior and plus-maze paradigm. The virilizing action of neonatally administered TP was demonstrated by dose-dependent delayed vaginal opening, a persistent estrus in their vaginal smears and the presence of polifollicular ovaries. Results are discussed on the bases of the differences and similarities between males, females, androgenized females and neonatally castrated males to anxiolytic steroids and the underlying possible processes.

A-ring reduced derivatives of two synthetic progestins induce anxiolytic effects in ovariectomized rats.

The putative anxiolytic action of the synthetic progestins, norethisterone (NET), levonorgestrel (LNG) and their respective 5 alpha-reduced metabolites, (5 alpha-NET), (3 alpha,5 alpha-NET), (3 beta,5 alpha-NET), (5 alpha-LNG), (3 alpha,5 alpha-LNG) and (3 beta,5 alpha-LNG), were studied in the burying behavior paradigm. From these compounds only 3 alpha,5 alpha-NET and 3 beta,5 alpha-LNG reduced burying behavior without modifying other parameters. Burying behavior latency was prolonged after administration of the highest dose (1.0 mg/rat) of NET and 5 alpha-NET. As a positive control 3 alpha,5 alpha-pregnanolone (allopregnanolone) was included at the same doses used for synthetic steroids. This steroid produced a clear dose-dependent reduction in burying behavior without affecting latency. No steroid with anxiolytic properties affected the general ambulatory behavior. All synthetic steroids with anxiolytic activity proved to be less potent than allopregnanolone. Results are discussed on the basis of the chemical structure requirements necessary to induce tranquilizing effects.

Blockade of the anxiolytic action of 8-OH-DPAT in lactating rats.

The anxiolytic action of 8-OH-DPAT (0.125, 0.5, and 0.75 mg/kg, I.P., -15 min) was evaluated in ovariectomized and 7-day lactating mother rats. This serotonergic anxiolytic produces a clear reduction in cumulative burying behavior and in freezing time (parameters denoting a reduction in anxiety levels) in ovariectomized subjects. However, in 7-day lactating mother rats, 8-OH-DPAT lacked its antianxiety effects. Additionally, as an extra parameter of the animal's emotionality the number of defecation bolus was registered. A reduction in this parameter in ovariectomized animals after 8-OH-DPAT (0.5 mg/kg) injection was found. This effect was also blocked in 7-day lactating rats. None of the doses of the compound tested altered the burying behavior latency (a parameter inversely representing the animal's reactivity). The general ambulatory behavior of ovariectomized subjects was significantly impaired at the highest dose (0.75 mg/kg) of 8-OH-DPAT. Lower doses did not alter this parameter or the number of times lines are crossed (a parameter denoting exploratory activity). Discussion is focused on the relationship between the activity of the serotonergic system and the secretion of prolactin in this period.

Anxiolytic actions of diazepam, but not of buspirone, are influenced by gender and the endocrine stage.

The effect of diazepam (1.0 mg/kg, i.p.) and buspirone (5.0 mg/kg, i.p.) on the burying behaviour latency (denoting actions on the animals' reactivity) and on the cumulative burying behaviour (directly reflecting the experimental anxiety levels), were analyzed in male-, intact females, at proestrus and metoestrus, and in neonatally-androgenized-rats. Androgenization was performed by injecting 60 micrograms/rat of testosterone propionate on day 5 after delivery. Two main groups of neonatally-androgenized rats were established: A group of animals showing permanent oestrus from the vaginal opening (acyclic females) and a group presenting the delayed anovulatory syndrome. Diazepam produced a clear reduction in experimental anxiety in males and neonatally-androgenized-females. Particularly important was the anxiolytic effect of diazepam on acyclic females that was accompanied by a significant increase in burying behaviour latency. Conversely, buspirone induced a clear reduction in burying behaviour, without modifying its latency, in all groups regardless of the gender and the neonatal treatment. Data are discussed on the basis of the androgen participation on the anxiolytic drug effects. A possible age-related benzodiazepine actions in females is suggested.