Behavioral differences between subgroups of rats with high and low threshold to clonic convulsions induced by DMCM, a benzodiazepine inverse agonist

Apitoxin alleviates methyl mercury-induced peripheral neurotoxicity in male rats by regulating dorsal root ganglia neuronal degeneration and oxidative stress

Methylmercury (MeHg) toxicity is associated with extensive neuronal degeneration of dorsal root ganglia (DRG). This study aimed to assess the ameliorative effect of bee venom (BV) on methyl mercury chloride (MeHgCl)-induced peripheral neurotoxicity using DRGs in rats. Forty-eight adult male Sprague Dawley rats were allocated into four equal groups: G I: control (gavaged MilliQ water 1 ml/rat), G II: subcutaneously injected with BV (0.5 mg/kg b.wt), G III: gavaged MeHgCl (6.7 mg/kg b.wt), and G IV: received MeHgCl+BV. Dosing was done five times/week for 2 weeks. Ataxic behavior and visual impairments were significantly increased, whereas the movement behavior and motility gait were suppressed in the MeHgCl group. MeHgCl significantly decreased total antioxidant capacity (TAC) in DRG and significantly decreased the serum levels of glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD). Tumor necrosis factor-alpha (TNF-α) and interleukin 1β (IL-1β) levels were significantly elevated, whereas interleukin 10 (IL-10) levels were significantly decreased in the MeHgCl group compared with the control group. DRGs of the MeHgCl-exposed rats showed pyknotic shrunken neurons with perineural vacuolations, demyelination of nerve axons, and proliferation of the satellite cells. MeHgCl significantly induced a higher positive index ratio of Iba-1, SOX10, neurofilament, pan-neuron, and vimentin immunostaining in the DRG. BV administration significantly mitigated the MeHgCl-induced alterations in oxidative stress-related indices. BV modified the immunostaining of Iba-1, SOX10, neurofilament, pan-neuron, and vimentin-positive index ratio in the DRG of the MeHgCl group. Our findings acknowledged that BV could enhance in vivo neuroprotective effects against MeHgCl-induced DRGs damage in male rats.

Alhagi maurorum Ethanolic Extract Rescues Hepato-Neurotoxicity and Neurobehavioral Alterations Induced by Lead in Rats via Abrogating Oxidative Stress and the Caspase-3-Dependent Apoptotic Pathway

This work investigated the probable protective effect of an Alhagi maurorum ethanolic extract on the hepatotoxicity and neurotoxicity accompanied by neurobehavioral deficits caused by lead in rats. Rats in four groups were orally administered distilled water, ethanolic extract of A. maurorum (300 mg/kg BW daily), lead (100 mg/kg BW daily for 3 months), and lead + A. maurorum extract. The results demonstrated that lead exposure resulted in elevated locomotor activities and sensorimotor deficits associated with a decrease in brain dopamine levels. Moreover, lead exposure significantly increased liver function markers. In addition, the lead-treated rats exhibited extensive liver and brain histological changes and apoptosis. The lead treatment also triggered oxidative stress, as demonstrated by the increase in malondialdehyde (MDA) concentrations with a remarkable reduction in the activities of antioxidant enzymes, reduced glutathione (GSH) levels, and transcriptional mRNA levels of antioxidant genes in the liver and brain. Nevertheless, co-treatment with the A. maurorum extract significantly ameliorated the lead-induced toxic effects. These findings indicate that the A. maurorum extract has the ability to protect hepatic and brain tissues against lead exposure in rats through the attenuation of apoptosis and oxidative stress.

Imidacloprid-based commercial pesticide causes behavioral, biochemical, and hematological impairments in Wistar rats

Imidacloprid (IMI) is a neonicotinoid insecticide employed worldwide for crop protection. IMI's mode of action occurs through the agonism of postsynaptic nicotinic acetylcholine receptors (nAChRs), with high specificity for insect nAChRs although there are reports of mammals' toxicity. Studies on IMI's neurotoxicity are not conclusive; therefore, the aim of this study was to evaluate the subchronic toxic effects of an IMI based commercial pesticide on rats. Adult male Wistar rats received an IMI suspension via the oral route at doses of 1.5, 5, and 15 mg/kg for 45 consecutive days. IMI caused an increase in rearing and time spent at the periphery in the locomotor activity test and a decrease in time spent to finish the OX maze task (p < 0.05; ANOVA/Bonferroni). In blood, there was a decrease in mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration (p < 0.05; ANOVA/Bonferroni) and an increase in serum butyrylcholinesterase activity (p < 0.001; ANOVA/Bonferroni). Therefore, subchronic administration of an IMI-based-pesticide caused behavioral and systemic impairments in rats.

Sustained Functioning Impairments and Oxidative Stress with Neurobehavioral Dysfunction Associated with Oral Nicotine Exposure in the Brain of a Murine Model of Ehrlich Ascites Carcinoma: Modifying the Antioxidant Role of Chlorella vulgaris

Simple Summary

Nicotine is the major psychoactive component considered to underlie tobacco’s addictive nature, and its dependence has been linked to several drawbacks on behavior and brain health. The purpose of this study was to investigate the mechanisms triggered by oral nicotine that cause brain tissue damage, as well as the supportive role of Chlorella vulgaris microalgae supplementation in Ehrlich ascites carcinoma in mice. The results revealed pronounced neurobehavioral alterations, increased mortality rate, oxidative stress, DNA damage, and augmented inflammatory response in the brain tissue alongside the microstructural alteration caused by nicotine. Chlorella vulgaris was quite successful in reducing the negative effects of nicotine. It acts as an antioxidant anti-inflammatory and restores nearly normal tissue architectures. As a result, we believe it should be supplemented to cancer patients consuming regular nicotine doses.

Abstract

Background: This study provides a model for studying the mechanism(s) responsible for the nervous tissue damage and misfunctioning that occurred due to oral nicotine exposure, considered a stress factor, during the presence of Ehrlich ascites carcinoma bearing in the mouse model (EAC). The mitigating role of Chlorella vulgaris (CV) against nicotine-induced brain damage was evaluated. Methods: Eighty Swiss female mice were classified into four groups, these were the control, the CV group, the nicotine group(100 µg/kg), and the combination group. Oxidant/antioxidant status, proinflammatory cytokines levels, DNA damage, quantitative microscopical lesions, and Caspase 3, Bcl-2 proteins were assessed in the current study. Levels of dopamine (DA) and gamma-aminobutyric acid (GABA) were also evaluated. Results: Nicotine was found to cause pronounced neurobehavioral alterations, increase the mortalities oxidative stress DNA damage, and augment the inflammatory response in brain tissue alongside the microstructural alteration. The administration of CV with nicotine in EAC-bearing mice rescued the detrimental effects of nicotine. Conclusions: CV aids in reducing the harmful effects of nicotine and returns the conditions caused by nicotine to near-control levels. Thus, we are in favor of giving it to cancer patients who are taking daily dosages of nicotine even by smoking cigarettes or being exposed to second-hand smoke.

Bee venom Apis mellifera lamarckii rescues blood brain barrier damage and neurobehavioral changes induced by methyl mercury via regulating tight junction proteins expression in rat cerebellum

The objective of the current study is to investigate the protective effect of Egyptian bee venom (BV) against methyl mercury chloride (MMC) induced blood-brain barrier (BBB) damage and neurobehavioral changes. Eighty male Sprague-Dawley rats were randomly grouped into 1st control (C), 2nd BV (0.5 mg/kg S/C for14 days), 3rd MMC (6.7 mg/kg orally/14 days), and 4th MMC + BV group. MMC exposure significantly altered rat cognitive behavior, auditory startle habituation, and swimming performance, increased the exploratory, grooming, and stereotypic behavior. MMC significantly impaired BBB integrity via induction of inflammation, oxidative stress, and down-regulation of tight junction proteins genes (TJPs) mRNA expression levels: Occludin (OCC), Claudins-5 (CLDN5), Zonula occludens-1 (ZO-1), while up-regulated the transforming growth factor-beta (TGF-β) mRNA expression levels. MMC revealed a significantly higher percentage of IgG positive area ratio, a higher index ratio of Iba1, Sox10, and ss-DNA, while index ratio of CD31, neurofilament, and pan neuron showed a significant reduction. Administration of BV significantly regulates the MMC altered behavioral responses, TJPs relative mRNA expression, and the immune-expression markers for specific neural cell types. It could be concluded for the first time that BV retains a promising in vivo protection against MMC-induced BBB dysfunction and neurobehavioral toxicity.

Curcumin mitigates neurotoxic and neurobehavioral changes of gentamicin and sodium salicylate in rats by adjusting oxidative stress and apoptosis

Currently, antibiotics and salicylates are the most highly consumed medications worldwide. The side effects of these pharmaceuticals on the nervous system have been little investigated. Thus, this study aimed to examine the influence of the gentamicin (GM) and sodium salicylates (SS) on neurobehavioral functions, including locomotors function, memory, and sensorimotor functions together with gamma-aminobutyric acid (GABA) neurotransmitter levels. Also, oxidative stress, lipid peroxidation, and apoptotic indicators of brain tissue were assessed. Additionally, the histopathological architecture of brain tissues was investigated. This study also evaluated the curcumin (CUR) efficacy to counteract the GM or SS induced neurotoxic impacts in rats. For this purpose, seven groups were administered physiological saline (1 ml/rat; orally), olive oil (1 ml/rat; orally), CUR (50 mg/kg bwt; orally), GM (120 mg/kg bwt; intraperitoneally), SS (300 mg /kg bwt; intraperitoneally), CUR + GM, or CUR + SS for consecutive 15 days. The results revealed that GM and SS exposure evoked impaired memory, sensorimotor deficit functions, and depressive-like behavior together with the depletion of GABA. GM and SS exposure elevated malondialdehyde and Caspase-3 levels, but total antioxidant capacity and Bcl-2 levels were reduced. Besides, GM and SS exposure induced distinct pathological perturbations in cerebral cortices and hippocampus tissues. CUR significantly reversed the GM and SS harmful impacts. In conclusion, these findings verified that CUR could be a biologically efficient protective intervention against GM and SS induced neurotoxic impacts and neurobehavioral aberrations.

Anti-Inflammatory, Anti-Arthritic and Anti-Nociceptive Activities of Nigella sativa Oil in a Rat Model of Arthritis

This study investigated the preventive efficacy of the crude oil extracted from Nigella sativa seeds in a rat model of arthritis induced by using complete Freund’s adjuvant (CFA). Nigella sativa oil at 1.82 mL/kg or 0.91 mL/kg (corresponding to 1596 and 798 mg/kg, respectively) was orally administered for 25 days from the day of immunization. One immunized group was treated orally with indomethacin (3 mg/kg) as a reference drug. Body weight growth rate, paw swelling, arthritis score, mechanical allodynia, locomotor activity and anxiety-like behavior were observed, and the levels of Interleukin 6 (IL-6), C-reactive protein, albumin and total cholesterol in plasma were measured on days 15 and 25. Nigella sativa oil showed anti-inflammatory, anti-arthritic and anti-nociceptive activities that were significant as compared to untreated arthritic rats but less than indomethacin. These results indicated that Nigella sativa oil significantly attenuated adjuvant-arthritis in rats and the higher dose (1.82 mL/kg) prevented the development of arthritis with an inhibition of 56%.

Spirulina platensis attenuates the associated neurobehavioral and inflammatory response impairments in rats exposed to lead acetate

Heavy metals are well known as environmental pollutants with hazardous impacts on human and animal health because of their wide industrial usage. In the present study, the role of Spirulina platensis in reversing the oxidative stress-mediated brain injury elicited by lead acetate exposure was evaluated. In order to accomplish this aim, rats were orally administered with 300 mg/kg bw Spirulina for 15 d, before and simultaneously with an intraperitoneal injection of 50 mg/kg bw lead acetate [6 injections through the two weeks]. As a result, the co-administration of Spirulina with lead acetate reversed the most impaired open field behavioral indices; however, this did not happen for swimming performance, inclined plane, and grip strength tests. In addition, it was observed that Spirulina diminished the lead content that accumulated in both the blood and the brain tissue of the exposed rats, and reduced the elevated levels of oxidative damage indices, and brain proinflammatory markers. Also, because of the Spirulina administration, the levels of the depleted biomarkers of antioxidant status and interleukin-10 in the lead-exposed rats were improved. Moreover, Spirulina protected the brain tissue (cerebrum and cerebellum) against the changes elicited by lead exposure, and also decreased the reactivity of HSP70 and Caspase-3 in both cerebrum and cerebellum tissues. Collectively, our findings demonstrate that Spirulina has a potential use as a food supplement in the regions highly polluted with heavy metals.

Imidacloprid insecticide exposure induces stress and disrupts glucose homeostasis in male rats

In the present study, we evaluated the stress response in adult rats who were administered imidacloprid (IMI) orally in two doses (0.5 and 1.0mg/kg bw for 60days). It led to an alteration in the levels of cortisone and catecholamines and induced behavioral deficits, particularly in the animals exposed to the dose of 1.0mg/kg. IMI was further analyzed for the effect on glucose homeostasis in developing and adult rats at a dose of 1.0mg/kg bw where it elicited a hyperglycemic effect. Moreover, we observed an alteration in the mRNA levels of glucose transporters. Histopathological and immunohistochemical data displayed structural perturbations in pancreatic tissue with a decline in the expression of insulin and GLUT4, particularly in the developing rats. Collectively, IMI treatment resulted in stress represented by behavioral and biochemical changes, particularly at a dose of 1.0mg/kg bw. Moreover, IMI perturbed the glucose regulation through hyperglycemic activity in both developing and adult rats, an observation clearly evident in the developing rats.

Neurodevelopmental consequences of gestational and lactational exposure to pyrethroids in rats

Indiscriminate use of pyrethroids has raised serious health related concerns, especially about their effects on children. The present study was designed to assess the developmental neurotoxicity of two pyrethroids; bifenthrin (BIF) and β-cyfluthrin (CYF) administered at 1/15 of LD₅₀ in rats. Pregnant females were exposed to the test compounds orally throughout gestation and lactation periods. Neonates were weighed and sexed at birth and were observed for any gross abnormality. Growth, viability and weaning indices were calculated during the lactation period. Exposure to both the compounds did not alter the physical developmental parameters viz. eye opening, pinna detachment, and fur appearance. CYF significantly impaired growth and survivability of pups. Behavioral endpoints assessed in neonates (surface righting, pivoting, and negative geotaxis reflex) as well as adults (motor activity and motor coordination) exhibited marked effect of CYF treatment. Administration of BIF to pregnant dams impaired pivoting in neonates. Decreased locomotion in the open-field and impaired rota-rod performance were also witnessed in BIF-exposed animals. Enhanced oxidative stress was seen in corpus striatum, cerebellum, and hippocampus regions of the brain; reduced catalase, superoxide dismutase, and glutathione peroxidase activities were measured in BIF and CYF treated weanlings. Acetylcholinesterase activity was also found to be lowered following administration of both compounds at PND 21. The present results suggest that exposure to pyrethroids during critical periods of growth can induce long term effects on the behavior of animals. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1761-1770, 2016.

Ontogenic profile of seizures evoked by the beta-carboline DMCM (methyl-6,7-dimethoxy-4-ethyl-β-carboline-3-carboxylate) in rats

The beta-carboline, methyl-6,7-dimethoxy-4-ethyl-β-carboline-3-carboxylate (DMCM), is a potent chemoconvulsant. While it has been utilized in adult rodents, it has not been previously examined for effects across postnatal development. DMCM is a negative allosteric modulator of benzodiazepine-sensitive GABAA receptors, receptor subtypes that are particularly enriched in limbic brain regions. This raises the possibility that DMCM may be particularly effective at evoking forebrain seizures, which is a challenge in neonatal animals due to the relative immaturity of the forebrain seizure network. The ability to selectebrain seizures is desirable when screening for drugs to use in temporal lobe epilepsy, which is characterized by seizures within the forebrain (limbic) network. To determine the profile of DMCM action across development, we examined the dose-dependent ability of DMCM to induce seizures in rats at P7, P10, P13, P14, P21 and in adulthood. We found that the highest sensitivity to DMCM occurred in P10, P13, and P14 rats. The lowest sensitivity occurred in P21 rats. Neonatal (P7) and adult (P60+) rats displayed moderate sensitivity. With moderate (0.2-0.4 mg/kg) doses of DMCM, we were able to reliably evoke limbic motor seizures without tonic-clonic components in animals as young as P7. These data support the utility of DMCM in assessing seizure threshold during development and raise the possibility for future exploration of DMCM as an agent to screen anticonvulsant drugs during the postnatal period.

Rats with different thresholds for DMCM-induced clonic convulsions differ in the sleep-time of diazepam and [(3)H]-Ro 15-4513 binding

The current study investigated the possible inherent relationship between convulsions and sleep involving the GABA(A)/benzodiazepine site complex. The aim of this study was to determine if rats with high (HTR) and low (LTR) thresholds for clonic convulsions induced by DMCM, a benzodiazepine inverse agonist, differ in the following aspects: (1) sensitivity to the hypnotic effects of the GABA(A) positive allosteric modulators diazepam, pentobarbital and ethanol and (2) in the binding of [(3)H]-flunitrazepam, a benzodiazepine agonist, measured by autoradiography, and [(3)H]-Ro 15-4513, a benzodiazepine partial inverse agonist, to membranes from discrete brain regions. The LTR subgroup presented a shorter diazepam-induced sleeping time compared to that of the HTR subgroup. Biochemical assays revealed that the LTR subgroup did not differ in [(3)H]-flunitrazepam binding compared to the HTR subgroup. With respect to the binding of [(3)H]-Ro 15-4513, the LTR subgroup had higher binding in the brainstem and lower binding in the striatum compared to the HTR subgroup. These results suggest that differences in the benzodiazepine site on the GABA(A) receptor may underlie the susceptibility to DMCM-induced convulsions and sensitivity to the hypnotic effect of diazepam.

Potential of a Khaya ivorensis -Alstonia boonei extract combination as antimalarial prophylactic remedy

ETHNOPHARMACOLOGICAL RELEVANCE

The decoction of the combined stem barks of Khaya ivorensis A. Chev. (Meliaceae) and Alstonia boonei De Wild (Apocynaceae) has a history of use in traditional medicine of central Cameroon for malaria treatment but also for the prevention of the disease.

AIM OF THE STUDY

The purpose of this investigation was to determine the antiplasmodial activity of Khaya ivorensis (K) and Alstonia boonei (A) preparations in the murine malaria model Plasmodium berghei/Anopheles stephensi, to estimate their prophylactic potential and to assess acute and sub-acute toxicity of the formulations prepared according to the traditional recipes.

MATERIALS AND METHODS

Aqueous extracts from the stem-bark of the two plants were prepared and tested separately and in combination. BALB/c mice were treated for 9 days and challenged on day 3 by exposure to mosquitoes infected with Plasmodium berghei. Treatment doses ranged between 200 and 400mg/kg/day, corresponding approximately to the dosage applied by traditional healers to cure malaria patients or prevent the disease. Parasitemia reduction in treated animals was calculated from Giemsa smear counts, of two replicate experiments. To estimate acute toxicity in terms of median lethal dose (LD50), geometrically increasing doses were administered to mice. Sub-acute toxicity of the herbal combination (KA) was investigated by administering the same doses as in the antiplasmodial activity test for a period of 14 days, followed by 14 days of recovery observation. Locomotor activity (Open Field Test), body weight, liver and kidney morphology were monitored.

RESULTS

The combination KA was found to exhibit antiplasmodial activity in the murine malaria model. In mice treated with the combination remedy at a dosage of 200mg/kg/day, parasitemia values of 6.2% ± 1.7 and 6.5% ± 0.8 were recorded, compared to 10.8% ± 1.3 and 12.0% ± 4.0 in controls (p<0.01). Doubling the dosage of the extracts did not significantly increase parasite suppression. When extracts of K and A were administered separately at a dosage of 400mg/kg, a reduction in parasitemia was still obtained, but it did not reach statistical significance. Toxicity studies yielded comforting results: the LD50 was estimated to be greater than 2779.5mg/kg. Moreover, mice exposed to the fourteen-day repeated-dose toxicity test (sub-acute toxicity test) did not display weight loss, liver or kidney morphological modifications, significant alterations in locomotor activity or any other sign of illness.

CONCLUSION

The antiplasmodial activity and the wide dose interval between the therapeutic dosage and the toxic dosage exhibited by the KA herbal combination in the murine malaria model argue in favor of its use as an antimalarial prophylactic remedy. It remains to be demonstrated by human clinical trials whether the combination remedy, when taken by inhabitants during malaria transmission season, can reduce parasite density and lead to a reduction of malaria episodes in the community.

Ibuprofen and Lipoic Acid Diamide as Co-Drug with Neuroprotective Activity: Pharmacological Properties and Effects in β-Amyloid (1–40) Infused Alzheimer's Disease Rat Model

Both oxidative stress and inflammation are elevated in brains of Alzheimer's disease patients, but their pathogenic significance still remains unclear. Current evidence support the hypothesis that non-steroidal anti-inflammatory drugs (NSAIDs) and antioxidant therapy might protect against the development of Alzheimer's disease, and ibuprofen has the strongest epidemiological support. In the present work our attention was focused on (R)-α-lipoic acid considered as a potential neuroprotective agent in Alzheimer's disease therapy. In particular, we investigated a new co-drug (1) obtained by joining (R)-α-lipoic acid and ibuprofen via a diamide bond, for evaluating its potential to antagonize the deleterious structural and cognitive effects of β-amyloid (1–40) in an infused Alzheimer's disease rat model. Our results indicated that infusion of β-amyloid (1–40) impairs memory performance through a progressive cognitive deterioration; however, ibuprofen and co-drug 1 seemed to protect against behavioural detriment induced by simultaneous administration of β-amyloid (1–40) protein. The obtained data were supported by the histochemical findings of the present study: β-amyloid protein was less expressed in 1-treated than in ibuprofen and (R)-α-lipoic acid alone-treated cerebral cortex. Taken together, the present findings suggest that co-drug 1 treatment may protect against the cognitive dysfunction induced by intracerebroventricular infusion of β-amyloid (1–40) in rats. Thus, co-drug 1 could prove useful as a tool for controlling Alzheimer's disease-induced cerebral amyloid deposits and behavioural deterioration.

Molecular determinants of beta-carboline inhibition of the glycine receptor

beta-Carbolines are potent modulators of GABA type A receptors and they have recently been shown to inhibit glycine receptors in a subunit-specific manner. The present study screened four structurally similar beta-carbolines, 1,2,3,4-tetrahydronorharmane, norharmane, harmane and 6-methoxyharmalan, at recombinantly expressed alpha1, alpha1beta, alpha2 and alpha3 glycine receptors with the aims of identifying structural elements of both the receptor and the compounds that are important for binding and subunit specificity. The four compounds exhibited only weak subunit specificity, rendering them unsuitable as pharmacological probes. Because they displayed competitive antagonist activity, we investigated the roles of known glycine binding residues in coordinating the four compounds. The structural similarity of the compounds, coupled with the differential effects of C-loop mutations (T204A, F207Y) on compound potency, implied direct interactions between variable beta-carboline groups and mutated residues. Mutant cycle analysis employing harmane and norharmane revealed a strong pairwise interaction between the harmane methyl group and the C-loop in the region T204 and F207. These results which define the orientation of the bound beta-carbolines were supported by molecular docking simulations. The information may also be relevant to understanding the mechanism beta-carboline of binding to GABA type A receptors where they are potent pharmacological probes.

Similar anxiolytic-like effects following intra-amygdala infusions of benzodiazepine receptor agonist and antagonist: evidence for the release of an endogenous benzodiazepine inverse agonist in mice exposed to elevated plus-maze test

Previous studies have demonstrated that microinjections of midazolam, a benzodiazepine receptor agonist, into the amygdala produce anxiolytic-like effects in elevated plus-maze (EPM)-naïve rodents. However, systemic or intracerebral administration of benzodiazepines (BDZ) fails to alter anxiety in maze-experienced animals, a phenomenon defined as "one trial tolerance" (OTT). This study focused on the effects of intra-amygdala infusion of midazolam in maze-experienced mice. In addition, the effects of flumazenil in the amygdala of maze-naïve and experienced mice were also investigated. To investigate intrinsic effects of intra-amygdala flumazenil on anxiety, animals were systemically treated with the BDZ receptor inverse agonist, DMCM (4-ethyl-6,7-dimethoxy-9H-pyrido[3,4-b]indole-3-carboxylic acid methyl ester hydrochloride). Conventional measures of anxiety (% open arm entries and % open arm time), locomotor activity (frequency of closed arm entries) and a range of ethological measures related to risk assessment were recorded. Intra-amygdala midazolam (3.0 and 30 nmol) attenuated anxiety in maze-experienced mice. A similar behavioral profile was produced by intra-amygdala flumazenil in maze-naïve (4.0 and 16 nmol) and maze-experienced (16 nmol) mice. Intra-amygdala flumazenil (at 2.0 nmol, a dose devoid of any intrinsic effect on anxiety measures in the EPM) selectively and completely blocked the anxiogenic-like effects of systemic administration of DMCM (1.0 mg/kg, i.p.) in maze-naïve mice. Together, these results demonstrate that the GABA(A)-benzodiazepine receptor complex located within the amygdala does not play a role in the OTT phenomenon. Present results also suggest that the release of an endogenous BDZ receptor inverse agonist within the amygdala seems to be an important correlate of the emotional state induced by the plus-maze test.

Synthesis and Study ofl-Dopa−Glutathione Codrugs as New Anti-Parkinson Agents with Free Radical Scavenging Properties

A series of novel molecular combinations (1-4), in which L-dopa (LD) is linked covalently via an amide bond with glutathione (GSH), were synthesized and evaluated as potential anti-Parkinson agents with antioxidant properties. These conjugates were characterized by evaluating solubility, chemical and enzymatic stabilities, and apparent partition coefficient (log P). Derivatives 2 and 4 were tested for their radical scavenging activities, by use of a test involving the Fe(II)/H2O2-induced degradation of deoxyribose. In this study, the antioxidant efficacy of codrugs 1 and 3 was also assessed through the evaluation of plasmatic activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx). Furthermore, the central nervous effects and rat striatal concentration of LD and dopamine (DA) have been evaluated after oral administration of codrugs 1 and 3. Tested compounds prolonged the plasma LD levels and were able to induce sustained delivery of DA in rat striatum with respect to an equimolar dose of LD. The results suggest that compounds 1 and 3 could represent useful new anti-Parkinson agents devoid of the pro-oxidant effects associated with LD therapy and potentially able to restore the GSH depletion evidenced in the substantia nigra pars compacta (SNpc) of PD patients.

Rats bred for susceptibility to depression-like phenotypes have higher kainic acid-induced seizure mortality than their depression-resistant counterparts

Epidemiological evidence suggests that epilepsy and depression are comorbid diseases. In fact, depression is the most common neuropsychiatric disorder associated with epilepsy, particularly temporal lobe epilepsy, and individuals with a history of depression are at a higher risk for developing epilepsy than the general population. Despite the epidemiological evidence for this link, there has been little experimental evidence to support the connection or elucidate possible underlying mechanisms. In an effort to address this problem and develop an animal model of epilepsy and depression comorbidity, we assessed seizure susceptibility and severity parameters in rats selectively bred for either susceptibility (the SwLo, SUS, and HYPER lines) or resistance (the SwHi, RES, and MON RES lines) to depression-like phenotypes. We found that rats bred for susceptibility to depression-like phenotypes experienced higher mortality following kainic acid-induced seizures than their resistant counterparts. In contrast, most line differences were not recapitulated when flurothyl was used to elicit seizures. Stress reduced kainic acid-induced mortality rates in all lines except the HYPER rats, supporting previously established indications that the stress response of HYPER rats is abnormal. These combined results support a neurobiological link between epilepsy and depression, advancing us towards an animal model of their comorbidity.

Dopaminergic system modulation, behavioral changes, and oxidative stress after neonatal administration of pyrethroids

Pyrethroids are a class of insecticides involved in different neurological disorders. They cross the blood-brain barrier and exert their effect on dopaminergic system, contributing to the burden of oxidative stress in Parkinson's disease through several pathways. The aim of the present study was to evaluate the effect of neonatal exposition to permethrin and cypermethrin (1/10 of DL(50)) in rats from the eighth to the fifteenth day of life. Open-field studies showed increased spontaneous locomotor activity in the groups treated with permethrin and the one treated with cypermethrin, while a higher number of center entries and time spent in the center was observed for the cypermethrin-treated group. Lower dopamine and higher homovanillic acid levels were measured in the striatum from both treated groups. A reduction of blood glutathione peroxidase content was measured, while no change in blood superoxide dismutase was observed. Carbonyl group formation increased in striatum, but not in erythrocytes. Lipid peroxidation occurred in erythrocytes, but not in striatum. No changes in fluidity at different depths of plasma membrane were measured in striatum or erythrocytes. The activation of monocyte NADPH oxidase by phorbol esters (PMA) shows that superoxide anion production was reduced in the pyrethroid-treated groups compared to the control group. Our studies suggest that neonatal exposition to permethrin or cypermethrin induces long-lasting effects after developmental exposure giving changes in open-field behaviors, striatal monoamine level, and increased oxidative stress. Although the action of pyrethroids on various target cells is different, a preferential interaction with the extracellular side of plasma membrane proteins can be observed.