Differential neurobehavioral deficits induced by apomorphine and its oxidation product, 8-oxo-apomorphine-semiquinone, in rats

The Nitric Oxide (NO) Donor Molsidomine Attenuates Memory Impairments Induced by the D1/D2 Dopaminergic Receptor Agonist Apomorphine in the Rat

Several lines of evidence suggest that scarcity of the gaseous molecule nitric oxide (NO) is associated with the pathogenesis of schizophrenia. Therefore, compounds, such as NO donors, that can normalize NO levels might be of utility for the treatment of this pathology. It has been previously shown that the NO donor molsidomine attenuated schizophrenia-like behavioral deficits caused by glutamate hypofunction in rats. The aim of the current study was to investigate the efficacy of molsidomine and that of the joint administration of this NO donor with sub-effective doses of the non-typical antipsychotics clozapine and risperidone to counteract memory deficits associated with dysregulation of the brain dopaminergic system in rats. Molsidomine (2 and 4 mg/kg) attenuated spatial recognition and emotional memory deficits induced by the mixed dopamine (DA) D1/D2 receptor agonist apomorphine (0.5 mg/kg). Further, the joint administration of sub-effective doses of molsidomine (1 mg/kg) with those of clozapine (0.1 mg/kg) or risperidone (0.03 mg/kg) counteracted non-spatial recognition memory impairments caused by apomorphine. The present findings propose that molsidomine is sensitive to DA dysregulation since it attenuates memory deficits induced by apomorphine. Further, the current findings reinforce the potential of molsidomine as a complementary molecule for the treatment of schizophrenia.

Effects of semiquinone-rich surface on the behaviors of vascular cells

Dopamine has been widely used for surface modification of cardiovascular medical devices as it forms films on most substrates that provide functional groups for surface chemical modification. However, under oxidative stress, the phenolic hydroxyl group on dopamine can undergo reversible transformation into phenol-semiquinone-quinone, which can cause cytotoxicity and immunotoxicity. In this study, we measured the effects of semiquinone on the behavior of vascular wall cells and inflammatory cells under oxidative stress via ultraviolet irradiation with a hydrogen peroxide diluent. Na₂S₂O₃ was used as a stabilizer to obtain a semiquinone-rich poly-dopamine film, then phenol-semiquinone-quinone ratio on its surface was evaluated at three irradiation-oxidation time points. We found that the poly-dopamine film with ultraviolet irradiation in hydrogen peroxide solution for 15 min had the highest semiquinone occupancy of 19.18%. In the experimental group irradiated for 15 min, endothelial cells were cultured statically for 3 days and the number of surface adherent endothelial cells in the group with added semiquinone stabilizer was reduced to 73% of that in the group without stabilizer, indicating that semiquinone rich surface inhibits adhesion and proliferation of endothelial cells; Smooth muscle cells were cultured statically for 3 days, and the number of adherent smooth muscle on surfaces without stabilizer was reduced to 75% of that on surfaces with stabilizer added, indicating that semiquinone rich surfaces promote smooth muscle proliferation. These results demonstrate that semiquinone can adversely affect the repair effect after implantation of cardiovascular materials. Therefore, our study provides a reference for the application and optimization of dopamine in cardiovascular implant materials.

Photobiomodulation intervention improves oxidative, inflammatory, and morphological parameters of skeletal muscle in cirrhotic Wistar rats

Photobiomodulation (PBM) might be an intervention method to mitigate sarcopenia in cirrhotic patients. Given the lack of research on this issue, the goal of this study was to evaluate possible beneficial effects of PBM on the structural and functional properties of skeletal muscle from cirrhotic rats. Cirrhosis was induced by secondary bile duct ligation (BDL). Wistar rats were randomized into four groups: sham-operated control (Sham), Sham + PBM, BDL, and BDL + PBM. After cirrhosis induction, a dose of PBM (1 J; 100mW; 10 s; 880 nm; 6 × per week) was applied to each quadriceps, from the 15th to the 45th day after surgery. The locomotor ability was performed using an open-field task. The muscle structure was analyzed using histological methods. Cell damage was also evaluated assessing oxidative stress and DNA damage markers, and IL-1β pro-inflammatory interleukin by immunohistochemical analysis. An increase in the number of crossings was observed in the BDL + PBM group in relation to BDL. The BDL group showed muscle atrophy and increased IL-1β in relation to Sham, while in the BDL + PBM group, the fiber muscle was restructured and there was a decrease of IL-1 β. TBARS increased in the liver and muscle tissues in the BDL group and decreased it in the BDL + PBM group. SOD increased while CAT decreased in the BDL + PBM group in relation to the BDL group. No genotoxic or mutagenic effect was observed for PBM treatment. PBM improved the locomotion and the morphology of the muscle fibers, decreasing oxidative stress and inflammation, without causing DNA damage in cirrhotic rats.

The novel dehydroepiandrosterone (DHEA) derivative BNN27 counteracts cognitive deficits induced by the D1/D2 dopaminergic receptor agonist apomorphine in rats

RATIONALE

Schizophrenia is a devastating mental disease that affects nearly 1% of the population worldwide. It is well documented that the dopaminergic (DAergic) system is compromised in schizophrenia. It is of note that the mixed dopamine (DA) D₁/D₂ receptor agonist apomorphine induces schizophrenia-like symptoms in rodents, including disruption of memory abilities. Neuroactive steroids, comprising dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulphate (DHEAS), were shown to affect brain DAergic system and to be involved in schizophrenia. BNN27 is a novel DHEA derivative, which is devoid of steroidogenic activity. It has recently been reported that BNN27 counteracted schizophrenia-like behavioural deficits produced by glutamate hypofunction in rats.

OBJECTIVES

The aim of the present study was to investigate the ability of BNN27 to attenuate non-spatial, spatial recognition and discrete memory deficits induced by apomorphine in rats.

METHODS

To this end, the object recognition task (ORT), the object location task (OLT) and the step-through passive avoidance test (STPAT) were used.

RESULTS

BNN27 (3 and 6 mg/kg, i.p.) attenuated apomorphine (0.5 mg/kg, i.p.)-induced non-spatial, spatial recognition and discrete memory deficits. Interestingly, the effects of compounds on memory cannot be ascribed to changes in locomotor activity.

CONCLUSIONS

Our findings suggest that BNN27 is effective to DA dysfunction caused by apomorphine, attenuating cognitive impairments induced by this D1/D2 receptor agonist in rats. Additionally, our findings illustrate a functional interaction between BNN27 and the DAergic system that may be of relevance for schizophrenia-like behavioural symptoms.

Brain targeting of 9c,11t-Conjugated Linoleic Acid, a natural calpain inhibitor, preserves memory and reduces Aβ and P25 accumulation in 5XFAD mice

Deregulation of Cyclin-dependent kinase 5 (CDK5) by binding to the activated calpain product p25, is associated with the onset of neurodegenerative diseases, such as Alzheimer's disease (AD). Conjugated Linoleic Acid (CLA), a calpain inhibitor, is a metabolite of Punicic Acid (PA), the main component of Pomegranate seed oil (PSO). We have shown recently that long-term administration of Nano-PSO, a nanodroplet formulation of PSO, delays mitochondrial damage and disease advance in a mouse model of genetic Creutzfeldt Jacob disease (CJD). In this project, we first demonstrated that treatment of mice with Nano-PSO, but not with natural PSO, results in the accumulation of CLA in their brains. Next, we tested the cognitive, biochemical and pathological effects of long-term administration of Nano-PSO to 5XFAD mice, modeling for Alzheimer's disease. We show that Nano-PSO treatment prevented age-related cognitive deterioration and mitochondrial oxidative damage in 5XFAD mice. Also, brains of the Nano-PSO treated mice presented reduced accumulation of Aβ and of p25, a calpain product, and increased expression of COX IV-1, a key mitochondrial enzyme. We conclude that administration of Nano-PSO results in the brain targeting of CLA, and suggest that this treatment may prevent/delay the onset of neurodegenerative diseases, such as AD and CJD.

Neurobehavioral effects of vigabatrin and its ability to induce DNA damage in brain cells after acute treatment in rats

RATIONALE

Vigabatrin (VGB) is a drug indicated mostly for the treatment of spasms in childhood and West's syndrome patients. This drug inhibits irreversibly the enzyme GABA-transaminase (GABA-T), increasing GABA concentrations and enhancing GABAergic neurotransmission in the brain, which is known to induce behavioral changes.

OBJECTIVES

The aims of this study were to evaluate the effects of VGB in the short-term memory (STM), long-term memory (LTM), motivation, locomotion, and exploratory behavior tests and to detect deleterious or protective effects on DNA in target tissues of the drug.

METHODS

Male Wistar rats were treated with a single dose of VGB (100, 250, or 500 mg/kg) or saline solution before the inhibitory avoidance and open-field tasks. DNA damage was evaluated using the alkaline comet assay in peripheral blood, cerebral cortex, and hippocampus after behavioral testing.

RESULTS

There was no significant difference in the inhibitory avoidance task between the treated groups and the saline group. In all tested doses, VGB reduced the number of rearings in the open-field task. Besides, VGB 500 mg/kg affected locomotion, though it was not able to induce any DNA damage.

CONCLUSIONS

VGB did not affect STM and LTM, but the drug impaired the exploration and locomotion likely associated with its sedative effect. In addition, no DNA damage in cortex and hippocampus was detected after behavioral testing, when brain GABA levels are already increased.

(-)-Linalool, a naturally occurring monoterpene compound, impairs memory acquisition in the object recognition task, inhibitory avoidance test and habituation to a novel environment in rats

It is known that (-)-linalool is a competitive antagonist of NMDA receptors, which play a key role in the learning and memory processes; however, only a few studies have reported a possible interference of (-)-linalool in memory. The purpose of this study was to investigate the (-)-linalool effects on acquisition of short- and long-term memories through the objects recognition task, inhibitory avoidance test and habituation to a novel environment. Furthermore, the open field test was used to investigate the interference of (-)-linalool in motivation, locomotion and exploration by animals. Wistar male adult rats received an intraperitoneal injection (i.p.) of saline (NaCl 0.9%), tween 5% or (-)-linalool (50 or 100 mg/kg) before training in the tasks; MK-801 (0.1 mg/kg), a glutamate antagonist, was used as positive control. Short-term (STM) and long-term (LTM) memories were tested 1.5 and 24 h after training, respectively, in the inhibitory avoidance and recognition objects. The results suggested that (-)-linalool (as 50- and 100-mg/kg doses) impaired LTM acquisition, but not STM acquisition, in the object recognition task. In the inhibitory avoidance test, animals receiving linalool (both doses) showed impairment in acquisition of both memories measured. In the open field test, the animals that received (-)-linalool showed no significant difference in the crossings and latency to start the locomotion in any of the doses tested, although (-)-linalool 100 mg/kg reduced rearing behavior. When re-exposed to open field 24 h after training, the rats that received (-)-linalool 100mg/kg showed no habituation. Taken together, these data suggested that (-)-linalool was able to impair the acquisition of memory in rats, which can be associated to (-)-linalool antagonist capacity as regards NMDA glutamatergic receptors, since other glutamate antagonists also seem to affect memory.

Modulatory influence of dopamine receptors on consolidation of object recognition memory

The role of dopamine receptors in regulating the formation of recognition memory remains poorly understood. Here we show the effects of systemic administration of dopamine receptor agonists and antagonists on the formation of memory for novel object recognition in rats. In Experiment I, rats received an intraperitoneal (i.p.) injection of vehicle, the selective D1 receptor agonist SKF38393 (1.0 and 5.0mg/kg), or the D2 receptor agonist quinpirole (1.0 and 5.0mg/kg) immediately after training. In Experiment II, rats received an injection of vehicle, the dopamine receptor antagonist SCH23390 (0.1 and 0.05 mg/kg), or the D2 receptor antagonist raclopride (0.5 and 0.1mg/kg) before training, followed by an injection of vehicle or the nonselective dopamine receptor agonist apomorphine (0.05 mg/kg) immediately after training. SKF38393 at 5mg/kg produced an enhancement of novel object recognition memory measured at both 24 and 72 h after training, whereas the dose of 10mg/kg impaired 24-h retention. Posttraining administration of quinpirole did not affect 24-h retention. Apomorphine enhanced memory in rats given pretraining raclopride, suggesting that the effect was mediated by selective activation of D1 receptors. The results indicate that activation of D1 receptors can enhance recognition memory consolidation. Importantly, pharmacological activation of D1 receptors enhanced novel object recognition memory even under conditions in which control rats showed significant retention.

Systemic administration of doxorubicin impairs aversively motivated memory in rats

There is growing clinical evidence of cognitive impairment in cancer patients treated with chemotherapy, especially in women treated with drug combinations for breast cancer. Clinical studies have a difficult task of defining which drugs individually are responsible for the cognitive changes and published papers evaluating single agents in experimental models are scanty. In the present study we have investigated the effect of single escalating doses of doxorubicin (DOX) on memory for inhibitory avoidance conditioning (IA) in rats. The doses used were comparable to those applied in the clinic. When given systemically before training, higher doses of DOX impaired IA memory retention measured 24h and 7days, but not 3h after training. DOX did not affect IA retention when given either before or after training in a multiple-trial IA training protocol. Control experiments showed that DOX produced a decrease in exploratory behavior assessed by the number of rearings performed during exploration of an open field. The results indicate that a single systemic administration of DOX might impair long-term aversive learning.

beta-Lactotensin, a neurotensin agonist peptide derived from bovine beta-lactoglobulin, enhances memory consolidation in mice

beta-Lactotensin (His-Ile-Arg-Leu) is an ileum-contracting tetrapeptide isolated from bovine beta-lactoglobulin. We previously reported that a neurotensin agonist beta-lactotensin shows antinociceptive effect through neurotensin NT(2) receptor. We found that centrally or orally administered beta-lactotensin at a dose of 60nmol/mouse or 300-500mg/kg, respectively, increased memory consolidation in the step-through-type inhibitory avoidance test in mice. The memory-enhancing activity of beta-lactotensin was inhibited by the dopamine D(2) receptor antagonist raclopride but not the D(1) receptor antagonist SCH23390. Taken together, beta-lactotensin might improve memory consolidation through activating the dopamine D(2) receptor.

Gamma-decanolactone effect on behavioral and genotoxic parameters

Gamma-decanolactone is a monoterpene compound, which is shown to be active in some animal models. The psychopharmacological evaluation of this compound in mice has revealed that it has a dose-dependent effect on the central nervous system, including hypnotic, anticonvulsant and hypothermic activities. The aim of the present study was to evaluate the effect of gamma-decanolactone at 0.1 and 0.3 g/kg on behavior parameters related to plus-maze, open field and forced swim tests. In addition, we investigated its genotoxic activity. Gamma-decanolactone at the dose of 0.3 g/kg, but not 0.1 g/kg, decreased the number of crossings and rearings and there were no significant differences among groups regarding the latency to start locomotion in open field. A single i.p. administration of gamma-decanolactone, at the higher, but not at lower dose used, was able to increase the exploratory activity in the test session (24 h after training), as assessed by the number of rearings performed in open field, and induced DNA damage on brain tissue as measured in comet assay, suggesting an impairment of nonassociative, nonaversive learning and a genotoxic effect on CNS. Gamma-decanolactone did not change the behavior of animals in plus-maze and forced swim tests, suggesting this compound shows no anxiolytic or antidepressant activity.

An organic selenium compound attenuates apomorphine-induced stereotypy in mice

Selenium compounds display neuroprotective activities mediated at least in part by their antioxidant actions. Oxidative damage has been implicated in psychiatric disorders including schizophrenia and bipolar disorder, and an alteration in expression of selenium-binding protein-1 (SELENBP-1) has been recently reported in both the blood and brain of schizophrenic patients. In the present study we examined the effects of the organic selenium compound 3'3-ditrifluoromethyldiphenyl diselenide [(F3CPhSe)2] on apomorphine-induced stereotypy in mice, an animal model of psychosis. Systemic administration of (F3CPhSe)2 at the highest dose used (25.0 micromol/kg in a 10.0 ml/kg injection volume) significantly reduced apomorphine-induced stereotyped behaviors. A series of control experiments showed that the same dose of (F3CPhSe)2 did not affect open-field behavior, habituation, or aversively motivated memory. The results indicate that organic selenium compounds should be further investigated as agents with possible antipsychotic properties.

Pharmacological activity of ruthenium complexes trans-[RuCl(2)(L)4] (l = nicotinic or i-nicotinic acid) on anxiety and memory in rats

Many biological properties have been attributed to ruthenium complex I (trans-[RuCl(2)(nic)(4)]) and ruthenium complex II (trans-[RuCl(2 )(i-nic)( 4)]) including nitric oxide synthase inhibition. In this study, we evaluated pharmacological effects of these complexes on anxiety and memory formation. Memory was evaluated with inhibitory avoidance and habituation to an open-field and anxiety was tested with elevated plus-maze. Adult male Wistar rats (250 to 350 g) received intraperitoneal injections of vehicle, ruthenium complex I (45.2, 90.4, or 180.7 mumol/kg), or ruthenium complex II (0.08, 4.5, or 13.6 mumol/kg) 30 min prior open-field training or elevated plus-maze test and 30 min or 0 h after training. No effects were observed in the anxiety parameters and habituation to an open-field. The ruthenium complexes impaired memory retention compared with vehicle group in the inhibitory avoidance, as when administrated 30 min prior as immediately after training. The memory impairment induced by ruthenium complexes may be due to their nitric oxide synthase inhibition capacity.

Non-associative learning and anxiety in rats treated with a single systemic administration of the gastrin-releasing peptide receptor antagonist RC-3095

The gastrin-releasing peptide receptor (GRPR) has been implicated in the modulation of emotionally-motivated memory. In the present study, we investigated the role of the GRPR on non-emotional, non-associative memory, and anxiety. Adult male Wistar rats were given a systemic injection of the GRPR antagonist [D-Tpi6, Leu(13) psi(CH2NH)-Leu14] bombesin (6-14) (RC-3095) (0.2, 1.0 or 5.0mg/kg) 30 min before exposure to an open field or an elevated plus maze. Habituation to the open field was tested in a retention trial carried out 24 h after the first exposure to the open field. Rats given RC-3095 at the doses of 1.0 or 5.0mg/kg showed impaired habituation. Animals treated with 5.0mg/kg of RC-3095 spent significantly more time in the closed arms of the elevated plus maze. No effects of RC-3095 on locomotion or exploratory behavior were observed. The results implicate the GRPR in the regulation of non-emotional, non-associative memory as well as in anxiety.

Genotoxic, neurotoxic and neuroprotective activities of apomorphine and its oxidized derivative 8-oxo-apomorphine

Apomorphine is a dopamine receptor agonist proposed to be a neuroprotective agent in the treatment of patients with Parkinson's disease. Both in vivo and in vitro studies have shown that apomorphine displays both antioxidant and pro-oxidant actions, and might have either neuroprotective or neurotoxic effects on the central nervous system. Some of the neurotoxic effects of apomorphine are mediated by its oxidation derivatives. In the present review, we discuss recent studies from our laboratory in which the molecular, cellular and neurobehavioral effects of apomorphine and its oxidized derivative, 8-oxo-apomorphine-semiquinone (8-OASQ), were evaluated in different experimental models, i.e., in vitro genotoxicity in Salmonella/microsome assay and WP2 Mutoxitest, sensitivity assay in Saccharomyces cerevisiae, neurobehavioral procedures (inhibition avoidance task, open field behavior, and habituation) in rats, stereotyped behavior in mice, and Comet assay and oxidative stress analyses in mouse brain. Our results show that apomorphine and 8-OASQ induce differential mutagenic, neurochemical and neurobehavioral effects. 8-OASQ displays cytotoxic effects and oxidative and frameshift mutagenic activities, while apomorphine shows antimutagenic and antioxidant effects in vitro. 8-OASQ induces a significant increase of DNA damage in mouse brain tissue. Both apomorphine and 8-OASQ impair memory for aversive training in rats, although the two drugs showed a different dose-response pattern. 8-OASQ fails to induce stereotyped behaviors in mice. The implications of these findings are discussed in the light of evidence from studies by other groups. We propose that the neuroprotective and neurotoxic effects of dopamine agonists might be mediated, in part, by their oxidized metabolites.

Oxidative damage in brains of mice treated with apomorphine and its oxidized derivative

Increasing evidence suggests that some of the neurobiological and neurotoxic actions of apomorphine and other dopamine receptor agonists might be mediated by their oxidation derivatives. The aim of the present study was to evaluate the effects of apomorphine and its oxidation derivative, 8-oxo-apomorphine-semiquinone (8-OASQ), on oxidative stress parameters and antioxidant enzyme activity. Adult male CF-1 mice were treated with a systemic injection of apomorphine (0.4, 4.0 or 40.0 mg/kg) or 8-OASQ (0.4, 4.0 or 40.0 mg/kg). Animals were sacrificed by decapitation 24 h after treatment, and the forebrains were collected for analysis of thiobarbituric acid reactive species, protein carbonyls, the total radical-trapping antioxidant parameter, catalase and superoxide dismutase. These treatments did not induce lipid peroxidation at any dose tested. In contrast, apomorphine induced an increase in protein carbonylation and a decrease in total radical-trapping antioxidant parameter at all doses tested. 8-OASQ induced an increase in protein carbonylation and a decrease in total radical-trapping antioxidant parameter only at the higher dose tested. All apomorphine doses tested induced an increase in catalase, but not superoxide dismutase activities. In contrast, 8-OASQ induced a dose-dependent increase in CAT activity. The results suggest that apomorphine and its oxidation product, 8-OASQ, induce differential effects on CNS oxidative parameters.

β-Phenylethylamines and the isoquinoline alkaloids

This review covers beta-phenylethylamines and isoquinoline alkaloids derived from them, including further products of oxidation. condensation with formaldehyde and rearrangement, some of which do not contain an isoquinoline system, together with naphthylisoquinoline alkaloids, which have a different biogenetic origin. The occurrence of the alkaloids, with the structures of new bases, together with their reactions, syntheses and biological activities are reported. The literature from July 2002 to June 2003 is reviewed, with 568 references cited.

DNA damage in brain cells of mice treated with an oxidized form of apomorphine

We investigated whether systemic injection of apomorphine and its oxidation derivative 8-oxo-apomorphine-semiquinone (8-OASQ) could induce DNA damage in mice brain, using the single-cell gel assay. 8-OASQ induced DNA damage in the brains at 1 and 3 h, but not at 24 h after treatment whereas apomorphine induced a slight increase in brain DNA damage frequency at 3 h after treatment, suggesting that both drugs display genotoxic activity in brain tissue.