Agmatine attenuates acquisition but not the expression of ethanol conditioned place preference in mice: a role for imidazoline receptors

Filgrastim, a Recombinant Form of Granulocyte Colony-stimulating Factor, Ameliorates 3-nitropropionic Acid and Haloperidol-induced Striatal Neurotoxicity in Rats

Striatal neurotoxicity is the pathological hallmark for a heterogeneous group of movement disorders like Tardive dyskinesia (TD) and Huntington's disease (HD). Both diseases are characterized by progressive impairment in motor function. TD and HD share common features at both cellular and subcellular levels. Filgrastim, a recombinant methionyl granulocyte colony-stimulating factor (GCSF), shows neuroprotective properties in in-vivo models of movement disorders. This study seeks to evaluate the neuroprotective effect of filgrastim in haloperidol and 3-NP-induced neurotoxicity in rats. The study was divided into two: in study one, rats were administered with haloperidol for 21 days, filgrastim at the dose of (20, 40, 60 µg/kg,s.c.) was administered once a day before haloperidol treatment and the following parameters (orofacial movements, rotarod, actophotometer) were performed to assess TD. Similarly, in the second study, rats were administered with 3-NP for 21 days, filgrastim at a dose of (20 and 40 µg/kg, s.c.) was administered, and the following parameters (rotarod, narrow beam walk, and open field test) were assessed for HD. On the 22nd day, animals were sacrificed and cortex and striatum isolated for oxidative stress (LPO, GSH, SOD, catalase, and nitrate) marker assessment. Results revealed that haloperidol and 3-NP treatment significantly impaired motor coordination, and oxidative defense inducing TD and HD-like symptoms. Treatment with filgrastim significantly averted haloperidol and 3-NP-induced behavioral and biochemical alterations. Conclusively, the neuroprotective effect of filgrastim is credited to its antioxidant properties. Hence, filgrastim might be a novel therapeutic candidate for the management of TD and HD.

Agmatine prevents development of tolerance to anti-nociceptive effect of ethanol in mice

Drug tolerance is directly correlated with drug abuse and physical dependence. The development of tolerance is manifested as the decline in pharmacological responses of drugs following repeated administration of the constant dose. The present study evaluated the effect of agmatine in ethanol-induced anti-nociception and tolerance in the tail-flick assay in mice. In an acute protocol, ethanol (1 and 2 g/kg, i.p. [intraperitoneally]) and agmatine (20 and 40 μg/mouse, i.c.v. [intracerebroventricularly]) produced significant analgesic effects in mice, as was evident from the increased baseline tail-flick latency when tested 20 minutes after their administration. Agmatine in a per se non-effective dose (5 μg/mouse, i.c.v.), L-arginine (40 μg/mouse, i.c.v.), and arcaine (25 μg/mouse, i.c.v.) significantly potentiated the anti-nociceptive effect of ethanol. Blood ethanol analysis showed no significant differences in blood ethanol concentration between ethanol/saline- and ethanol/agmatine-treated mice, suggesting that the effects of agmatine were not due to any possible effects on the pharmacokinetics of ethanol. In a separate study, mice were injected with ethanol (2 g/kg, i.p., 12%) or saline (1 mL/kg, i.p.) once daily for 9 days. On days 1, 3, 5, 7, and 9 of the experiment, they were subjected to the tail-flick test. Agmatine (5-20 μg/mouse, i.c.v.), L-arginine (40 μg/mouse, i.c.v.), arcaine (25 μg/mouse, i.c.v.), aCSF (2 μL/mouse, i.c.v.), or saline (1 mL/kg, i.p.) was administered daily prior to the first daily ethanol or saline injections, and reaction latencies were determined in the tail-flick assay. Injections of agmatine, L-arginine, and arcaine prevented the development of tolerance to ethanol-induced analgesia. Given that agmatine and its endogenous modulation can prevent tolerance to the anti-nociceptive effects of ethanol, these data suggest it as a possible new therapeutic strategy for the treatment of alcohol use disorder and associated complications.

Effects of imidazoline agents in a rat conditioned place preference model of addiction

Agmatine (AG), idazoxan (IDZ), and efaroxan (EFR) are imidazoline receptor ligands with beneficial effects in central nervous system disorders. The present study aimed to evaluate the interaction between AG, IDZ, and EFR with an opiate, tramadol (TR), in a conditioned place preference (CPP) paradigm. In the experiment, we used five groups with 8 adult male Wistar rats each. During the condition session, on days 2, 4, 6, and 8, the rats received the drugs (saline, or TR, or IDZ and TR, or EFR and TR, or AG and TR) and were placed in their least preferred compartment. On days 1, 3, 5, and 7, the rats received saline in the preferred compartment. In the preconditioning, the preferred compartment was determined. In the postconditioning, the preference for one of the compartments was reevaluated. TR increased the time spent in the non-preferred compartment. AG decreased time spent in the TR-paired compartment. EFR, more than IDZ, reduced the time spent in the TR-paired compartment, but without statistical significance. AG reversed the TR-induced CPP, while EFR and IDZ only decreased the time spent in the TR-paired compartment, without statistical significance.

Inhibitory influence of agmatine in ethanol withdrawal-induced depression in rats: Behavioral and neurochemical evidence

Although ethanol withdrawal depression is one of the prominent reasons for ethanol consumption reinstatement and ethanol dependence, its neurochemical basis is not clearly understood. The present study investigated the role of the agmatinergic system in ethanol withdrawal-induced depression using the forced swim test (FST) in rats. Chronic exposure of animals to ethanol for 21 days and its abrupt withdrawal produced depression-like behavior, as evidenced by increased immobility time in the FST, compared to the pair-fed control animals. The ethanol withdrawal-induced depression was significantly attenuated by agmatine (20-40 μg/rat, i.c.v. [intracerebroventricularly]), moxonidine (50 μg/rat, i.c.v.), 2-BFI (20 μg/rat, i.c.v.), L-arginine (80 μg/rat, i.c.v.), amino-guanidine (25 μg/rat, i.c.v.), and arcaine (50 μg/rat, i.c.v.) by their once-daily administration during the withdrawal phase (Days 21, 22, and 23). The antidepressant effect of agmatine in ethanol-withdrawn rats was potentiated by the imidazoline receptor I₁ agonist moxonidine (25 μg/rat, i.c.v.) and the imidazoline receptor I₂ agonist, 2-BFI (10 μg/rat, i.c.v.) at their sub-effective doses. On the other hand, it was completely blocked by the imidazoline receptor I₁ antagonist, efaroxan (10 μg/rat, i.c.v.) and the imidazoline receptor I₂ antagonist, idazoxan (4 μg/rat, i.c.v.). In addition, agmatine levels were significantly reduced in brain samples of ethanol-withdrawn rats as compared to the pair-fed control animals. In conclusion, the present study suggests the importance of the endogenous agmatinergic system and the imidazoline receptors system in ethanol withdrawal-induced depression. The data project agmatine as a potential therapeutic target for the alcohol withdrawal-induced depression.

Agmatine: multifunctional arginine metabolite and magic bullet in clinical neuroscience?

Agmatine, the decarboxylation product of arginine, was largely neglected as an important player in mammalian metabolism until the mid-1990s, when it was re-discovered as an endogenous ligand of imidazoline and α2-adrenergic receptors. Since then, a wide variety of agmatine-mediated effects have been observed, and consequently agmatine has moved from a wallflower existence into the limelight of clinical neuroscience research. Despite this quantum jump in scientific interest, the understanding of the anabolism and catabolism of this amine is still vague. The purification and biochemical characterization of natural mammalian arginine decarboxylase and agmatinase still are open issues. Nevertheless, the agmatinergic system is currently one of the most promising candidates in order to pharmacologically interfere with some major diseases of the central nervous system, which are summarized in the present review. Particularly with respect to major depression, agmatine, its derivatives, and metabolizing enzymes show great promise for the development of an improved treatment of this common disease.

Dipeptidyl-peptidase IV (DPP-IV) inhibitor delays tolerance to anxiolytic effect of ethanol and withdrawal-induced anxiety in rats

Dipeptidyl-peptidase IV (DPP-IV) is an enzyme responsible for the metabolism of endogenous gut-derived hormone, glucagon-like peptide-1 (GLP-1). DPP-IV is known for its role in energy homeostasis and pharmacological blockade of this enzyme is a recently approved clinical strategy for the management of type II diabetes. Accumulating evidences suggest that enzyme DPP-IV can affect spectrum of central nervous system (CNS) functions. However, little is known about the role of this enzyme in ethanol-mediated neurobehavioral complications. The objective of the present study was to examine the impact of DPP-IV inhibitor, sitagliptin on the development of tolerance to anxiolytic effect of ethanol and anxiety associated with ethanol withdrawal in rats. A dose-response study revealed that sitaglitpin (20 mg/kg, p.o.) per se exhibit anxiolytic effect in the elevated plus maze (EPM) test in rats. Tolerance to anxiolytic effect of ethanol (2 g/kg, i.p.; 8 % w/v) was observed from 7(th) day of ethanol-diet (6 % v/v) consumption. In contrast, tolerance to anxiolytic effect of ethanol was delayed in rats that were treated daily with sitagliptin (20 mg/kg, p.o.) as tolerance was observed from 13(th)day since commencement of ethanol-diet consumption. Discontinuation of rats from ethanol-diet after 15-days of ethanol consumption resulted in withdrawal anxiety between 8 h and 12 h post-abstinence. However, rats on 15-day ethanol-diet with concomitant sitagliptin (20 mg/kg, p.o.) treatment exhibited delay in appearance (24 h post-withdrawal) of withdrawal anxiety. In summary, DPP-IV inhibitors may prove as an attractive research strategy against ethanol tolerance and dependence.

Agmatine protects against zymosan-induced acute lung injury in mice by inhibiting NF-κB-mediated inflammatory response

Acute lung injury (ALI) is characterized by overwhelming lung inflammation and anti-inflammation treatment is proposed to be a therapeutic strategy for ALI. Agmatine, a cationic polyamine formed by decarboxylation of L-arginine, is an endogenous neuromodulator that plays protective roles in diverse central nervous system (CNS) disorders. Consistent with its neuromodulatory and neuroprotective properties, agmatine has been reported to have beneficial effects on depression, anxiety, hypoxic ischemia, Parkinson's disease, and gastric disorder. In this study, we tested the effect of agmatine on the lung inflammation induced by Zymosan (ZYM) challenge in mice. We found that agmatine treatment relieved ZYM-induced acute lung injury, as evidenced by the reduced histological scores, wet/dry weight ratio, and myeloperoxidase activity in the lung tissue. This was accompanied by reduced levels of TNF-α, IL-1β, and IL-6 in lung and bronchoalveolar lavage fluid and decreased iNOS expression in lung. Furthermore, agmatine inhibited the phosphorylation and degradation of IκB and subsequently blocked the activation of nuclear factor (NF)-κB induced by Zymosan. Taken together, our results showed that agmatine treatment inhibited NF-κB signaling in lungs and protected mice against ALI induced by Zymosan, suggesting agmatine may be a potential safe and effective approach for the treatment of ALI.