Procognitive, Anxiolytic, and Antidepressant-like Properties of Hyperoside and Protocatechuic Acid Corresponding with the Increase in Serum Serotonin Level after Prolonged Treatment in Mice

Two polyphenols-hyperoside (HYP) and protocatechuic acid (PCA) were reported to exert antidepressant activity in rodents after acute treatment. Our previous study also showed that this activity might have been influenced by the monoaminergic system and the upregulation of the brain-derived neurotropic factor (BDNF) level. A very long-term pharmacological therapy is required for the treatment of a patient with depression. The repetitive use of antidepressants is recognized to impact the brain structures responsible for regulating both emotional and cognitive behaviors. Thus, we investigated the antidepressant, anxiolytic, and procognitive effects of HYP and PCA in mice after acute and prolonged treatment (14 days). Both polyphenols induced an anxiogenic-like effect after acute treatment, whereas an anxiolytic effect occurred after repetitive administration. PCA and HYP showed procognitive effects when they were administered acutely and chronically, but it seems that their influence on long-term memory was stronger than on short-term memory. In addition, the preset study showed that the dose of 7.5 mg/kg of PCA and HYP was effective in counteracting the effects of co-administered scopolamine in the long-term memory impairment model induced by scopolamine. Our experiments revealed the compounds have no affinity for 5-HT1A and 5-HT2A receptors, whereas a significant increase in serum serotonin level after prolonged administration of PCA and HYP at a dose of 3.75 mg/kg was observed. Thus, it supports the involvement of the serotonergic system in the polyphenol mechanisms. These findings led us to hypothesize that the polyphenols isolated from Impatiens glandulifera can hold promise in treating mental disorders with cognitive dysfunction. Consequently, extended studies are necessary to delve into their pharmacological profile.

Characteristics of Seltorexant-Innovative Agent Targeting Orexin System for the Treatment of Depression and Anxiety

Twenty-five years have passed since the discovery of the orexin system, during which time we have learned more and more about it. A number of studies have been conducted showing the role of the orexin system in insomnia, as well as its potential use in the treatment of obesity and depression. In this review, we present the role of the orexin system in the development of depressive illness and show the characteristics of seltorexant, a potential drug for the treatment of depression. This review describes the structure and synthesis of the compound as well as its pharmacodynamics and pharmacokinetics. Pre-clinical and clinical studies are also described, including side effects. There is evidence that the use of seltorexant is considered safe, with no clear or major clinically significant side effects, which makes it a promising candidate for the treatment of depression and anxiety disorders.

Recent Studies on the Development of Nicotine Abuse and Behavioral Changes Induced by Chronic Stress Depending on Gender

Nowadays, stressful situations are an unavoidable element of everyday life. Stressors activate a number of complex mental and physiological reactions in the organism, thus affecting the state of health of an individual. Stress is the main risk factor in the development of mental disorders, such as depression and other disorders developing as a result of addiction. Studies indicate that women are twice as likely as men to develop anxiety, depression and therefore addiction, e.g., to nicotine. Even though the data presented is indicative of significant differences between the sexes in the prevalence of these disorders, the majority of preclinical animal models for investigating stress-induced disorders use predominantly male subjects. However, the recent data indicates that this type of studies has also been launched in female rodents. Therefore, conducting research on both sexes allows for a more accurate understanding and assessment of the impact of stress on stress-induced behavioral, peripheral and molecular changes in the body and brain. In this manuscript we have gathered the data from 41 years (from 1981-2022) on the influence of stress on the development of depression and nicotine addiction in both sexes.

A Comprehensive Review of Daridorexant, a Dual-Orexin Receptor Antagonist as New Approach for the Treatment of Insomnia

Insomnia affects 4.4-4.8% of the world's population, but because the effect of hypnotic drugs is limited and may cause harmful side-effects, scientists are turning their attention to developing drugs that act on the orexin system. Daridorexant, a selective dual-orexin receptor antagonist (DORA), has exhibited promising results in both animal and human studies. Its activity was evaluated based on the physiology-based pharmacodynamic and pharmacokinetic model. The use of daridorexant is considered safe, with no clinically significant side-effects including deprivation of next-morning residual effects. In this manuscript we conducted a comprehensive review of daridorexant including pharmacodynamics, animal and human research, pharmacokinetics and safety.

Effect of Berberine Isolated from Barberry Species by Centrifugal Partition Chromatography on Memory and the Expression of Parvalbumin in the Mouse Hippocampus Proper

Neurodegenerative diseases associated with memory disturbances are important health issues occurring due to a prolonged life span. This article presents the results of a study targeting the emergence of a drug candidate with antiamnesic properties. The effect of berberine (BBR), an isoquinoline alkaloid isolated from the overground parts of Berberis sibirica Pall., on memory and expression of parvalbumin in the mouse hippocampus proper were determined. High-purity BBR was isolated by centrifugal partition chromatography from a methanolic extract from B. sibirica by using a methyl-tert-butyl ether and water (1:1 v/v) solvent system with 10 mmol/L of triethylamine and hydrochloric acid. In an in vivo study, we assessed the influence of the chronic administration of BBR on different stages of memory-related responses in mice. Our results indicated that the chronic administration of BBR in a higher dose (5 mg/kg) improves long-term memory acquisition in mice, as determined in the passive avoidance test. The hippocampal CA1–CA3 fields showed an increased number of parvalbumin-immunoreactive neurons (PV-IR) and nerve fibers as compared to the control. No significant changes in the dentate gyrus were observed between the groups. The HPLC-ESI-QTOF-MS/MS analysis of the biological material revealed the content of BBR as 363.4 ± 15.0 ng (4.11% of RSD) per brain, 15.06 ± 0.89 ng (5.91% of RSD) per hippocampus, and 54.45 ± 1.40 (4.05% of RSD) ng in 100 µL plasma. The study showed that BBR could be a factor influencing the expression of PV in hippocampal neurons. We speculate that BBR may modulate the level of Ca²⁺ in neurons and thus potentially act as a neuroprotective factor against neuronal damages.

N-(3-{4-[3-(trifluoromethyl)phenyl]piperazin-1-yl}propyl)-1H-indazole-3-carboxamide (D2AAK3) as a potential antipsychotic: In vitro, in silico and in vivo evaluation of a multi-target ligand

Schizophrenia is a mental illness of not adequately understood causes that is not satisfactorily enough treated by current antipsychotics. In search for novel potential antipsychotics we performed structure-based virtual screening aimed to identify new dopamine D₂ receptor antagonists. We found compound D2AAK3 with affinity to dopamine D₂ receptor of 115 nM. D2AAK3 possesses additional nanomolar or low micromolar affinity to D₁, D₃, 5-HT_1A, 5-HT_2A and 5-HT₇ receptors, which makes it a good hit for further development as a multifunctional ligand. The compound has also some affinity to M₁ and H₁ receptors. We used homology modeling, molecular docking and molecular dynamics to study interactions of D2AAK3 with its molecular targets at the molecular level. In behavioral studies D2AAK3 decreases amphetamine-induced hyperactivity (when compared to the amphetamine-treated group) measured as spontaneous locomotor activity in mice. In addition, passive avoidance test demonstrated that D2AAK3 improves memory consolidation after acute treatment in mice. Elevated plus maze tests indicated that D2AAK3 induces anxiogenic activity 30 min after acute treatment, whereas this effect has no longer been observed 60 min after administration of the studied compound in mice.

Response of immature rats to a low dose of nanoparticulate silver: Alterations in behavior, cerebral vasculature-related transcriptome and permeability

The increasing production and use of silver nanoparticles (AgNPs) as antimicrobial agents in medicinal and commercial products creates a substantial risk of exposure, especially for infants and children. Our current knowledge concerning the impact of AgNPs on developing brain is insufficient. Therefore we investigated the temporal profile of transcriptional changes in cellular components of the neurovascular unit in immature rats exposed to a low dose of AgNPs. The behavior of animals under these conditions was also monitored. Significant deposition of AgNPs in brain of exposed rats was identified and found to persist over the post-exposure time. Substantial changes were noted in the transcriptional profile of tight junction proteins such as occludin and claudin-5, and pericyte-related molecules such as angiopoietin-1. Moreover, downregulation of platelet-derived growth factor (PDGFβ) and its receptor (PDGFβR) which constitute the main signaling pathway between endothelial cells and pericytes was observed. These were long-lasting effects, accompanied by overexpression of astroglial-specific GFAP mRNA and endothelial cell adhesion molecule, ICAM-1, involved in the pathomechanism of neuroinflammation. The profile of changes indicates that even low doses of AgNPs administered during the early stage of life induce dysregulation of neurovascular unit constituents which may lead to disintegration of the blood-brain barrier. This was confirmed by ultrastructural analysis that revealed enhanced permeability of cerebral microvessels resulting in perivascular edema. Changes in the behavior of exposed rats indicating pro-depressive and anti-anxiety impacts were also identified. The results show a high risk of using AgNPs in medical and consumer products dedicated for infants and children.

Identification of a Potent and Selective 5-HT1A Receptor Agonist with In Vitro and In Vivo Antinociceptive Activity

Opioids are the gold standard drugs for the treatment of acute and chronic severe pain, although their serious side effects constitute a big limitation. In the search for new and safer drugs, 5-HT_1AR agonists are emerging as potential candidates in pain relief therapy. In this work, we evaluated the affinity and activity of enantiomers of the two newly synthesized, potent 5-HT_1AR agonists N-[(2,2-diphenyl-1,3-dioxolan-4-yl)methyl]-2-[2-(pyridin-4-yl)phenoxy]ethan-1-ammonium hydrogenoxalate (rac-1) and N-((2,2-diphenyl-1,3-dioxolan-4-yl)methyl)-2-(2-(1-methyl-1H-imidazol-5-yl)phenoxy)ethan-1-ammonium hydrogenoxalate (rac-2) in vitro and in vivo. The role of chirality in the interaction with 5-HT_1AR was evaluated by molecular docking. The activity of the rac-1 was tested in mouse models of acute pain (hot plate) and severe tonic nociceptive stimulation (intraplantar formalin test). Rac-1 was active in the formalin test with a reduction in paw licking in both phases at 10 mg/kg, and its effect was abolished by the selective 5-HT_1AR antagonist, WAY-100635. The eutomer (S)-1, but not the racemate, was active during the hot plate test at 10 and 20 mg/kg, and this effect was abolished by 30 min treatment with WAY-100635 at 30 min. Similarly to 8-OH-DPAT, (S)-1 evoked a slow outward current and depressed spontaneous glutamatergic transmission in superficial dorsal horn neurons, more effectively than rac-1. The eutomer (S)-1 showed promising developability properties, such as high selectivity over 5-HT subtypes, no interaction with the μ receptors, and low hepato- and cardiotoxicity. Therefore, (S)-1 may represent a potential candidate for the treatment of acute and chronic pain without having the adverse effects that are commonly associated with the classic opioid drugs.

Bergapten Improves Scopolamine-Induced Memory Impairment in Mice via Cholinergic and Antioxidative Mechanisms

Bergapten is a furanocoumarin naturally occurring in the Apiaceae family and it is a well-known photosensitizing agent used in photochemotherapy. In this study, we investigated the influence of bergapten on cognitive function and mechanism underlying these effects in scopolamine-induced memory impairment in male Swiss mice. The passive avoidance test was used to evaluate the efficiency of memory acquisition and consolidation. The results demonstrated that both single and repeated administration of bergapten improved not only the acquisition but also consolidation of memory. The behavioral tests showed that bergapten prevented memory impairment induced by administration of scopolamine. Observed effects may result from the inhibition of acetylcholinesterase activity in the hippocampus and prefrontal cortex. Also, bergapten caused significant anti-oxidative effects. These new findings provide pharmacological and biochemical support for the development of the coumarin’s potential in cognitive deficits.

N-(2-Hydroxyphenyl)-1-[3-(2-oxo-2,3-dihydro-1H- benzimidazol-1-yl)propyl]piperidine-4-Carboxamide (D2AAK4), a Multi-Target Ligand of Aminergic GPCRs, as a Potential Antipsychotic

N-(2-hydroxyphenyl)-1-[3-(2-oxo-2,3-dihydro-1H-benzimidazol -1-yl)propyl]piperidine-4-carboxamide (D2AAK4) is a multitarget ligand of aminergic G protein-coupled receptors (GPCRs) identified in structure-based virtual screening. Here we present detailed in vitro, in silico and in vivo investigations of this virtual hit. D2AAK4 has an atypical antipsychotic profile and low affinity to off-targets. It interacts with aminergic GPCRs, forming an electrostatic interaction between its protonatable nitrogen atom and the conserved Asp 3.32 of the receptors. At the dose of 100 mg/kg D2AAK4 decreases amphetamine-induced hyperactivity predictive of antipsychotic activity, improves memory consolidation in passive avoidance test and has anxiogenic properties in elevated plus maze test (EPM). Further optimization of the virtual hit D2AAK4 will be aimed to balance its multitarget profile and to obtain analogs with anxiolytic activity.

The influence of bilberry fruit on memory and the expression of parvalbumin in the rat hippocampus

Therefore, the aim of the present study was to evaluate the possible effect of bilberry fruit (Vaccinium myrtillus L.) supplement in a daily diet on the cognitive behaviour of the rats and the expression of paravalbumin (PV) in populations of hippocampal neurons. It has been postulated that the antioxidants present in bilberry fruit may act as neuroprotective factors playing also a significant role as memory enhancements. Forty Wistar rats with a similar average body weight (460 ± 0.4 g) were divided into four groups (n=10 per group). The control group received standard feed (210 g/week), whereas animals of experimental groups received standard feed supplemented with bilberry (per os) at consumed doses of 2 g (group I), 5 g (group II), and 10 g/kg b.w./ /day (group III). After three months of feeding with bilberry, the modified elevated plus-maze test (mEPM) was performed. After 32 weeks of feeding, brains were collected and PV-immunoreactive (ir) neurons were immunohistochemically visualized. In the modified elevated plus-maze test, transfer latency examined 2 h and 24 h after the acquisition session was significantly shorter (p⟨0.05) in the group II in comparison with the control group. In CA1 and CA2/CA3 hippocampal fields as well as dentate gyrus of all experimental groups, a significant (p⟨0.05) decrease in number of PV-ir neurons were found. In relation to the control group, the mean subpopulation of PV-ir neurons found in groups II and III were significantly reduced. The subpopulations of PV-ir neurons found in DG of all experimental groups were significantly reduced in comparison to the control. In conclusion the in the present paper we demonstrated a relationship between the diet rich in a bilberry fruit and process of memory as well as numbers of calcium- binding protein-expressing hippocampal neurons. Our results may be source of basic knowledge for further research aiming at neuroprotective role of the bilberry fruit.

Mephedrone Impact on Matrix Metalloproteinases Activity - Do they Influence the Memory Processes?

BACKGROUND

The use of drugs of addiction, as mephedrone, is associated with functional neuronal disorders due to remodeling of the nervous tissue. Key enzymes in remodeling are extracellular matrix (ECM) proteases like matrix metalloproteases (MMPs). Recently, MMPs have been of great interest as some studies point to a fact that the alterations in structural remodeling of synaptic connections modify learning-dependent changes, which remain active even after a prolonged period of abstinence. This entails a continuous development of dependence.

OBJECTIVES

The aim of the study was to determine the influence of subchronic exposure to three different doses of mephedrone on the activity of MMP-2 and 9 in hippocampus and prefrontal cortex and how this was correlated with memory processes in mice.

METHODS

The homogenates of hippocampus and cortex were assayed for MMP-2 and MMP-9 activity by gelatin zymography. Memory consolidation processes were evaluated in the passive avoidance (PA) test.

RESULTS

The study confirmed the dose-dependent increase in activity of MMP-2 and -9 exerted by subchronic administration of mephedrone. Moreover, the highest dose of mephedrone attenuated consolidation of memory and learning processes.

CONCLUSIONS

We could hypothesize that inhibition of MMPs can be considered as a therapeutic option for the treatment of addictive behaviors associated with cognitive processes. Moreover, further studies are required to find out if elevated activities of MMPs contribute to brain damage or recovery from brain damage caused directly by mephedrone.

Monoaminergic system is implicated in the antidepressant-like effect of hyperoside and protocatechuic acid isolated from Impatiens glandulifera Royle in mice

We have recently demonstrated that the hydroethanolic extracts of Impatiens glandulifera Royle (Balsaminaceae) have antianxiety effect in mice. The present study was aimed to investigate an antidepressant activity of hyperoside (HYP) and protocatechuic acid (PCA), two polyphenols isolated from the aerial parts of this plant, using the forced swimming test (FST) and tail suspension test (TST) in mice. The implication of the monoaminergic system in this effect was assessed and brain-derived neurotrophic factor (BDNF) expression was measured. At doses 1.875, 3.75 and 7.5 mg/kg, HYP and PCA significantly reduced immobility in the FST and TST, without affecting locomotor activity of mice. Pretreatment with p-chlorophenylalanine (PCPA 100 mg/kg, a serotonin synthesis inhibitor) or α-methyl-DL-tyrosine (AMPT 100 mg/kg, a catecholamine synthesis inhibitor) was able to prevent antidepressant-like effect of HYP and PCA (3.75 mg/kg). Sub-effective doses of fluoxetine (5 mg/kg) or reboxetine (2 mg/kg) were capable of potentiating the effect of a sub-effective dose of HYP (0.94 mg/kg) in the FST. Co-administration of sub-effective dose of PCA (0.94 mg/kg) and reboxetine (2 mg/kg) resulted in reducing immobility in the FST. The antidepressant-like effect of HYP and PCA was also prevented by the administration of sulpiride (50 mg/kg), a D2 antagonist. In addition, HYP (3.75 and 7.5 mg/kg) and PCA (7.5 mg/kg) improved the expression of hippocampal BDNF of mice subjected to TST. Altogether, our findings suggest that HYP and PCA exert antidepressant-like effects in mice, which was possibly mediated by monoaminergic system and the upregulation of BDNF level.

Potential pro-oxidative effects of single dose of mephedrone in vital organs of mice

BACKGROUND

Mephedrone is a recreationally used synthetic cathinone, relatively new abusive substances with molecular structure similar to amphetamine. As there is still lack of scientific data regarding mechanisms of action as well as metabolism of mephedrone, especially in aspects other than neurotoxicity, addiction or behavioral changes, therefore we aimed, for the first time, to investigate potential pro-oxidative actions of a single dose of mephedrone in organs other than brain and its structures, i.e. in liver, kidneys, heart and spleen of Swiss mice.

METHODS

The following biomarkers of oxidative stress were measured: concentration of ascorbic acid (AA) and malondialdehyde (MDA) as well as total antioxidant capacity (TAC) of the tissues homogenates.

RESULTS

Our study revealed that mephedrone intoxication induces oxidative stress by reducing concentration of AA and TAC and increasing concentration of MDA in these organs.

CONCLUSIONS

Such occurred state of antioxidant-oxidant imbalance may be etiopathological factor of a number of severe diseases within cardiovascular, digestive as well as immunological systems.

In vitro, molecular modeling and behavioral studies of 3-{[4-(5-methoxy-1H-indol-3-yl)-1,2,3,6-tetrahydropyridin-1-yl]methyl}-1,2-dihydroquinolin-2-one (D2AAK1) as a potential antipsychotic

Antipsychotics currently available to treat schizophrenia suffer several limitations: (1) they are efficient against positive but not negative and cognitive symptoms of the disease; (2) they help only a half of patients; (3) they have severe side effects including neurological and metabolic side effects. Thus, novel drugs to treat schizophrenia are highly demanded. We identified a novel dopamine D2 receptor antagonist, D2AAK1, with Ki of 58 nM using structure-based virtual screening. D2AAK1 possesses additional nanomolar or low micromolar affinity to D1, D3, 5-HT1A and 5-HT2A receptors, making it an ideal candidate for a multi-target drug. Here we present homology modeling, molecular docking and molecular dynamics of D2AAK1 and its molecular targets and animal studies of D2AAK1 as a potential antipsychotic. The main contact of D2AAK1 and all the receptors studied is the electrostatic interaction between the protonable nitrogen atom of the ligand and the conserved Asp(3.32) as typical for orthosteric ligands of aminergic GPCRs. We confirmed antagonistic/partial agonistic properties of D2AAK1 towards all the receptors in in vitro essays and in in silico studies as the ligand stabilizes the ionic lock interaction. We also demonstrated neuroleptic, anxiolytic and, importantly, procognitive properties of D2AAK1 in mouse models.

Rimonabant attenuates sensitization, cross-sensitization and cross-reinstatement of place preference induced by nicotine and ethanol

The present study focused on the evaluation of behavioral sensitization, cross-sensitization, and cross-reinstatement processes induced by nicotine and ethanol in rodents. First, we showed that nicotine (0.175 mg/kg, base, intraperitoneally, ip) produced a conditioned place preference in rats. When the nicotine place preference was extinguished, nicotine-experienced animals were challenged with nicotine (0.175 mg/kg, ip) or ethanol (0.5 g/kg, ip), which reinstated a preference for the compartment previously paired with nicotine. In the second series of experiments, we demonstrated that after 9 days of nicotine administration (0.175 mg/kg, subcutaneously, sc) every other day and following its 7-day withdrawal, challenge doses of nicotine (0.175 mg/kg, sc) and ethanol (2 g/kg, ip) induced locomotor sensitization in mice. Finally, when we examined the influence of rimonabant (0.5, 1 and 2 mg/kg, ip), we found that this cannabinoid CB₁ receptor antagonist attenuated reinstatement effect of ethanol priming as well as nicotine sensitization and locomotor cross-sensitization between nicotine and ethanol. Our results indicate that similar endocannabinoid-dependent mechanisms re involved in the locomotor stimulant and reinforcing effects of nicotine and ethanol in rodents, and as such these data may provide further evidence for the use of cannabinoid CB₁ receptor antagonists in treatment of tobacco addiction with or without concomitant ethanol dependence.

Memantine and ACPC affect conditioned place preference induced by cocaine in rats

The influence of uncompetitive NMDA receptor antagonist, 1-amino-3,5--dimethyl-adamantane (memantine) and partial glycineB site agonist, 1-amino-cyclopropanecarboxylic acid (ACPC) on cocaine-induced conditioned place preference (CPP) were examined in male Wistar rats. After determination of initial preference, animals were conditioned with cocaine (5 mg/kg, ip) for 3 conditioning trials, alone or in combination with memantine (7.5 mg/kg, ip) or ACPC (50.0 mg/kg, ip). Memantine prevented acquisition and expression of the place preference produced by cocaine, while ACPC prevented only acquisition effect. Neither of the NMDA antagonists displayed any reinforcing properties by itself. Our current data suggest that the NMDA receptor complex may be involved in the rewarding effect of cocaine.

Haloperidol-induced catalepsy is influenced by calcium channel antagonists

The effect of pretreatment of some voltage-dependent calcium channel antagonists was studied on haloperidol-induced catalepsy in male Wistar rats. Cataleptogenic effect of haloperidol (0.25 mg/kg, i.p.) was enhanced dose-dependently by nitrendipine (5, 10 and 20 mg/kg, i.p.) and the highest dose of nimodipine (20 mg/kg, i.p.). Neither verapamil (10 and 20 mg/kg, i.p.) nor diltiazem (10 and 20 mg/kg, i.p.) influenced the score of haloperidol-induced catalepsy in rats. These results suggest the involvement of calcium-dependent mechanisms in the generation of haloperidol-induced catalepsy. The possible involvement of dopaminergic mechanisms and modification by calcium channel antagonists are discussed.

Effects of the NMDA/glycine receptor antagonist, L-701,324, on morphine- and cocaine-induced place preference

Effects of the novel NMDA/glycine receptor antagonist, L-701,324, on morphine- and cocaine-induced conditioned place preference (CPP) were examined in male Wistar rats. After determination of initial preference, animals were conditioned with morphine (5 mg/kg, i.p.) or cocaine (5 mg/kg, i.p.) for 3 conditioning trials, alone or in combination of these drugs with L-701,324 (2.5 mg/kg and 5 mg/kg, p.o.). L-701,324 prevented acquisition of the place preference produced by morphine and cocaine. Administration of L-701,324 on the test day attenuated the expression of morphine-induced CPP, whereas it had no effect on cocaine CPP. When L-701,324 was given alone it did not affect dependent variables (i.e. time spent in non-preferred compartment) suggesting that L-701,324 did not display any reinforcing properties by itself. Our current data suggest that glycine site on the NMDA receptor complex may be involved in the mediation of the rewarding effects of drugs of abuse.

Effects of calcium channel ligands on anaesthetic properties of ethanol in mice

This study has examined the effect of two calcium channel antagonists--nifedipine, verapamil and a calcium channel agonist BAY K 8644 on duration of ethanol-induced anaesthetic activity measured as the loss of the righting reflex (LORR) in mice. Nifedipine (5 and 10 mg/kg, i.p.) and verapamil (10 and 20 mg/kg, i.p.) potentiated the acute general anaesthetic effect of ethanol (3.5 g/kg, i.p.). BAY K 8644 (2 mg/kg, i.p.) shortened the duration of ethanol-induced LORR. This action of BAY K 8644 was prevented by the pretreatment with nifedipine (2.5 mg/kg, i.p.) but not with verapamil (5 mg/kg, i.p.). Injections of both calcium channel blockers--nifedipine (2.5 mg/kg) and verapamil (5 mg/kg) did not influence the ethanol-induced hypnotic activity themselves. Our results suggest that the calcium ions are involved in the central depressant effects of acute ethanol administration at high doses. It can be supposed that the modification of the activity of voltage-dependent calcium channels plays an important role in the anaesthetic action of ethanol.

Blockade of the acquisition of ethanol-induced conditioned place preference by N-methyl-D-aspartate receptor antagonists

We have examined the influence of two different N-methyl-D-aspartate (NMDA) receptor antagonists on acquisition of the reinforcing properties of ethanol measured in the conditioned place preference (CPP) paradigm in rats. After receiving 15 daily injections of ethanol (0.5 g/kg, i.p.) before the conditioning trials, rats acquired the preference to the compartment paired with ethanol injections during conditioning. Both dizocilpine (0.1 mg/kg, i.p.), a non-competitive antagonist of the NMDA receptor, and L-701,324 (5 mg/kg, per os), an antagonist acting at the strychnine-insensitive glycine site of NMDA receptor complex, when co-administered repeatedly with ethanol, prevented the acquisition of ethanol-induced CPP. Dizocilpine alone provoked the development of CPP, having some intrinsic rewarding properties. In contrast, L-701,324 alone did not affect the CPP. These results suggest that the rewarding properties of ethanol could be, at least in part, due to its action at the NMDA receptor complex. Additionally, we can speculate that NMDA receptor antagonists can be useful in the treatment of ethanol dependence. Glycine receptor antagonists having no abuse potential might have advantages in terms of safety compared to non-competitive NMDA receptor antagonists.

Antidepressant-like properties of some serotonin receptor ligands and calcium channel antagonists measured with the forced swimming test in mice

This study has examined the effects of 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT), buspirone, nifedipine and verapamil on duration of immobility in the forced swimming test in mice. The 5-HT1A agonist-8-OH-DPAT (0.25, 0.5, 1 mg/kg) and dihydropyridine calcium channel antagonist-nifedipine (10 mg/kg) produced decreases in immobility time. These effects were similar to those of the tricyclic antidepressant-imipramine (5 and 10 mg/kg). Non-dihydropyridine calcium channel antagonist-verapamil (10 and 20 mg/kg) had no effect on immobility time. The non-benzodiazepine anxiolytic and 5-HT1A agonist-buspirone (1 mg/kg) when given in a single injection or as repeated treatment, did not exert antidepressant-like activity in the forced swimming test. Pretreatment with dopamine antagonist-haloperidol (0.5 mg/kg) significantly antagonized the effects of 8-OH-DPAT (1 mg/kg), imipramine (10 mg/kg) and nifedipine (10 mg/kg). Pretreatment with benzodiazepine anxiolytic-diazepam (2 mg/kg) antagonized the effect of imipramine (10 mg/kg) but not that of 8-OH-DPAT (1 mg/kg) or nifedipine (10 mg/kg). Neither haloperidol nor diazepam produced any effects in this test. Single or repeated administration of buspirone (1 mg/kg) did not alter the reduction of immobility time produced by imipramine (10 mg/kg). These results suggest that 5-HT1A agonists and dihydropyridine calcium channel blockers may have antidepressant efficacy in the forced swimming test, but the effects of buspirone and 8-OH-DPAT may be mediated via different mechanisms. These results also indicate that the relationship between serotonin and dopamine neurons may play a role in the action of antidepressant drugs. In addition, the interactions involving both GABAergic and serotoninergic processes exist between benzodiazepine anxiolytics and some antidepressants.

Effects of calcium channel antagonists on the reinforcing properties of morphine, ethanol and cocaine as measured by place conditioning

Morphine, ethanol and cocaine were examined in place conditioning paradigm. After initial preferences were determined, animals were conditioned with morphine (5 mg/kg), ethanol (1 g/kg) and cocaine (5 mg/kg) alone or combinations of these drugs plus some calcium antagonists: nifedipine (5 and 10 mg/kg) and verapamil (5 and 10 mg/kg). Nifedipine prevented the ability of morphine and cocaine, but not of ethanol, to produce a place preference. Our results suggest that substances which can influence calcium distribution are involved in the rewarding actions of some drugs-morphine and cocaine. Dihydropyridine, a calcium channel antagonists might be clinically useful for the treatment of morphine and cocaine abuse.

Rewarding properties of some drugs studied by place preference conditioning

Ethanol, morphine, cocaine and amphetamine were examined in place conditioning. After determination of initial preferences, animals were conditioned with ethanol (1 g/kg), morphine (5 mg/kg), cocaine (5 mg/kg) and amphetamine (5 mg/kg) alone or with combinations of these drugs plus naloxone (1 mg/kg). Naloxone prevented the ability of all drugs used to produce a place preference. The reinforcing properties of ethanol and morphine were reduced by sodium nitroprusside at a dose equal to 1/10 of LD50 given before preference testing. Molsidomine (1/10 LD50 and 1/20 LD50) altered the expression of the conditioned place preference produced by ethanol but not by morphine. Results of the present study suggest the involvement of endogenous opioids and probably of nitric oxide in the rewarding actions of drugs of abuse.