Alpha 2-adrenoceptor

2-methoxyidazoxan (RX 8210022) is a highly selective alpha 2-adrenoceptor antagonist with little or no imidazoline antagonist effect. RX821002 is a drug that elicits noradrenaline release in the cortex by blocking alpha2-adrenoautoreceptors in the locus coeruleus [1].

2-Methoxyidazoxan monohydrochloride/RX 821002 (1 mg/kg) improves the ability of rats with neonatal ventral hippocampal lesion (NVHL) to move about in new settings. 2-The effects of 2-methylidazoxan monohydrochloride on locomotion are biphasic, exhibiting a reduction at first before intensification [3].

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Rats with a neonatal ventral hippocampal lesion (NVHL) are used to model schizophrenia. They show enhanced locomotion and difficulties in learning after puberty. Such behavioral modifications are strengthened by dopaminergic psychostimulant drugs, which is also relevant for schizophrenia because illustrating its dopaminergic facet. But it remains questionable that only dopaminergic drugs elicit such effects. The behavioral effects could simply represent a non specific arousal, in which case NVHL rats should also be hyper-responsive to other vigilance enhancing drugs. We administered an adenosine (caffeine) or an adrenaline receptor antagonist, (RX 821002) at doses documented to modify alertness of rats, respectively 5 mg/kg and 1 mg/kg. Rats were selected prior to the experiments using magnetic resonance imaging (MRI). Each group contained typical and similar NVHL lesions. They were compared to sham lesioned rats. We evaluated locomotion in a new environment and the capacity to remember a visual or acoustic cue that announced the occurrence of food. Both caffeine and RX82100 enhanced locomotion in the novel environment, particularly in NVHL rats. But, RX82100 had a biphasic effect on locomotion, consisting of an initial reduction preceding the enhancement. It was independent of the lesion. Caffeine did not modify the learning performance of NVHL rats. But, RX 821002 was found to facilitate learning. Patients tend to intake much more caffeine than healthy people, which has been interpreted as a means to counter some cognitive deficits. This idea was not validated with the present results. But adrenergic drugs could be helpful for attenuating some of their cognitive deficits[3].

Four antagonists were examined for their ability to differentiate alpha 2A-from the orthologous alpha 2D-adrenoceptors. The antagonists were (2S,12bS)1',3'-dimethylspiro(1,3,4,5',6,6',7,12b-octah ydro-2H- benzo[b]furo[2,3-a]quinolizine)-2,4'-pyrimidin-2'-one (MK912), 2-[2-(methoxy-1,4-benzodioxanyl)imidazoline (RX 821002 ), efaroxan and benoxathian. The alpha 2-autoreceptors in rabbit brain cortex were chosen as alpha 2A-and the alpha 2-autoreceptors in guinea-pig brain cortex as alpha 2D-adrenoceptors. Slices of the brain cortex were preincubated with 3H-noradrenaline and then superfused and stimulated electrically by brief pulse trains (4 pulses, 100 Hz) that led to little, if any, alpha 2-autoinhibition. 5-Bromo-6-(2-imidazolin-2-ylamino)-quinoxaline (UK 14,304) was used as an alpha 2-adrenoceptor agonist. UK 14, 304 decreased the stimulation-evoked overflow of tritium. The antagonists shifted the concentration-inhibition curve of UK 14, 304 to the right in an apparently competitive manner. Dissociation constants of the antagonists were calculated from the shifts. MK 912, RX 821002 and efaroxan had markedly higher affinity for (guinea-pig) alpha 2D-adrenoceptors (pKd values 10.0, 9.7 and 9.1, respectively) than for (rabbit) alpha 2A-adrenoceptors (pKd 8.9, 8.2 and 7.6, respectively). Benoxathian had higher affinity for alpha 2A-(pKd 7.4) than for alpha 2D-adrenoceptors (pKd 6.9). Ratios calculated from the Kd values of the four compounds differentiated between alpha 2A and alpha 2D up to 100 fold. It is concluded that MK 912, RX 821002 , efaroxan and benoxathian are antagonists with high power to differentiate alpha 2A-from alpha 2D-adrenoceptors[2].

Selecting subjects using MRI imaging techniques[3]
Twenty-one day-old lesioned pups were subjected to an MRI session under isoflurane anesthesia. MRI was performed on a small-animal scanner operating at 4.7 T (TR/TE/TEeff: 3000/30 ms/60 ms). A series of 10 slices (256 × 256 pixels) was generated over a 1 cm long section of the brain, rostral to the cerebellum-cerebrum gap, as in our previous studies and those conducted by others (Angst et al., 2007; Macedo et al., 2008, 2010, 2012; Bertrand et al., 2010; Sandner et al., 2010, 2011, 2012), the purpose being to select triplets of lesioned rats (1 saline, 1 caffeine and 1 RX 821002), where each member of the triplet had about the same MRI image in terms of the location and symmetry of the lesion (examples are shown in Figure 1). We obtained 9 triplets of lesions (27 lesioned rats), to which we added 27 sham-lesioned controls. Rats that could not be included in a triplet were transferred to other research protocols.
Lesioned areas were drawn on MRI coronal sections. The numbers of pixels of the left and right lesions were summed up over successive rostro-caudal sections. The sum represents then the estimated volumes of the lesions. It was submitted to an ANOVA, with lesion side as within-group factor and treatment as between-group factor. Another ANOVA was computed on the sum of left and right lesions with the three rats in each triplet as within-group factor. The threshold for statistical significance for all statistical computations was set to p < 0.05.

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Treatments[3]
A 3 × 2 experimental design was used (6 groups of 9 rats). The treatment was applied before each test and each learning session. The latency between injection and the beginning of the test was 10 min for caffeine (5 mg/kg) and 20 min for RX 821002 (1 mg/kg), dissolved in saline (vehicle: veh) in a final volume of 1 ml and injected i.p. Control rats received a saline injection 10 or 20 min before testing. The following groups were considered: 9 NVHL rats treated with caffeine (caf group), 9 NVHL rats treated with RX 821002 (RX group), and 9 NVHL rats which were given saline (veh group), plus three groups of 9 sham-lesioned rats which received the same treatments.

[1]. Head GA. Importance of imidazoline receptors in the cardiovascular actions of centrally acting antihypertensive agents. Ann N Y Acad Sci. 1995;763:531-540.

[2]. Antagonists that differentiate between alpha 2A-and alpha 2D-adrenoceptors. Naunyn Schmiedebergs Arch Pharmacol. 1996;353(3):245-249.

[3]. Effects of caffeine or RX821002 in rats with a neonatal ventral hippocampal lesion. Front Behav Neurosci. 2014;8:15. Published 2014 Jan 28.

2-methoxyidazoxan is a benzodioxine that is idazoxan substituted at position 2 by a methoxy group. It has a role as an alpha-adrenergic antagonist. It is a benzodioxine, a cyclic ketal and a member of imidazolines. It is functionally related to an idazoxan.

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Adrenergic alpha-Antagonists: Drugs that bind to but do not activate alpha-adrenergic receptors thereby blocking the actions of endogenous or exogenous adrenergic agonists. Adrenergic alpha-antagonists are used in the treatment of hypertension, vasospasm, peripheral vascular disease, shock, and pheochromocytoma.

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Increasing evidence indicates that the hypotensive effect of centrally acting antihypertensive drugs is not due to stimulation of alpha 2-adrenoceptors but to action on imidazoline receptors (IR). This has led to the development and recent clinical use of second generation agents such as rilmenidine and moxonidine that possess a much greater selectivity toward these nonadrenergic receptors. However, relatively few studies have examined the role of these receptors in conscious animals or have adequately accounted for the alpha 2-adrenoceptor antagonist properties of IR antagonists such as idazoxan. We have taken the approach of initially calibrating the alpha 2-adrenoceptor antagonist potency of intracisternally (ic) administered idazoxan and the IR-1 receptor antagonist efaroxan against 2-methoxyidazoxan, a highly selective alpha 2-adrenoceptor antagonist with little or no imidazoline antagonist effect. This was done using alpha-methyldopa, a hypotensive agent affecting only alpha 2-adrenoceptors. Thus, we chose doses of the antagonists with equal alpha 2-adrenoceptor blocking action such that differences in the ability of idazoxan or efaroxan compared to 2-methoxy-idazoxan to reverse the hypotension produced by rilmenidine, moxonidine, or clonidine indicate an interaction with IR. By this method we found that the hypotensive effects of rilmenidine and moxonidine at moderate intracisternal doses were more readily reversed by the imidazoline antagonists than by 2-methoxy-idazoxan, indicating that IR were largely responsible for their hypotensive actions. By contrast, clonidine's effects were equally reversed by all antagonists, suggesting interaction mainly with alpha 2-adrenoceptors. In conscious rabbits with chronic renal sympathetic nerve electrodes we examined the effect of rilmenidine and alpha-methyldopa on the renal sympathetic baroreflex. Both drugs reduced renal sympathetic nerve activity and sympathetic baroreflex responses, but only the effect of rilmenidine was preferentially reversed by idazoxan. Thus, both IR and central alpha 2-adrenoceptor receptors can influence the renal baroreflex, but the former are relatively more important for the actions of rilmenidine. We recently examined the possible sites of action of rilmenidine in anesthetized rabbits and showed that sixfold lower doses were required to reduce blood pressure when the drug was injected into the rostral ventrolateral medulla compared to intracisternal administration. At this site rilmenidine also reduced renal sympathetic tone and inhibited renal sympathetic baroreflex responses. By contrast, rilmenidine was relatively ineffective when injected into the nucleus of the solitary tract. These experiments support the view that rilmenidine acts primarily at IR in the rostral ventrolateral medulla to reduce sympathetic tone and modulate sympathetic baroreflexes.[1]

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Contrasting with the lack of improvement in the performance of rats under caffeine, RX821002, the alpha2-adrenoreceptor antagonist, improved learning. Research about the contribution of noradrenergic systems to schizophrenia has yielded inconsistent results (van Kammen and Antelman, 1984; van Kammen and Kelley, 1991; Yamamoto et al., 1994; Friedman et al., 1999; Klimek et al., 1999). Interest has been shown, however, in the prefrontal noradrenergic mechanisms and the potential role of alpha-2-adrenoreceptor antagonism in the antipsychotic effects of atypical neuroleptics, particularly considering that co-medication of fluphenazine with the alpha-2-adrenoreceptor antagonist idazoxan enhanced its antipsychotic and cognitive effectiveness (Litman et al., 1996). Our results complement these observations, highlighting the importance of adrenoreceptors as targets for treating cognitive difficulties like those experienced by patients with schizophrenia (McAllister, 2001; Masana et al., 2011).[3]

C12H14N2O3

234.25

234.1

102575-24-6

109544-45-8 (HCl); 102575-24-6

108094

Typically exists as solid at room temperature

1.34g/cm3

407.9ºC at 760mmHg

200.5ºC

1.72E-06mmHg at 25°C

1.617

0.566

1

4

2

17

321

0

O1C2C=CC=CC=2OCC1(OC)C1NCCN=1

HQGWKNGAKBPTBX-UHFFFAOYSA-N

InChI=1S/C12H14N2O3/c1-15-12(11-13-6-7-14-11)8-16-9-4-2-3-5-10(9)17-12/h2-5H,6-8H2,1H3,(H,13,14)

2-(3-methoxy-2H-1,4-benzodioxin-3-yl)-4,5-dihydro-1H-imidazole

RX-821002; RX 821002; 2-Methoxyidazoxan; 102575-24-6; 1H-Imidazole, 2-(2,3-dihydro-2-methoxy-1,4-benzodioxin-2-yl)-4,5-dihydro-; alpha-methoxyidazoxan; 2-(3-methoxy-2H-1,4-benzodioxin-3-yl)-4,5-dihydro-1H-imidazole; RX821002

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)