human GAT-1 (IC50 = 14 μM); rat GAT-1 (IC50 = 39 μM); rat GAT-2 (IC50 = 58 μM); human GAT-3 (IC50 = 119 μM); rat GAT-3 (IC50 = 378 μM)

Guvacine HCl has IC50s of 14 μM (human GAT-1), 39 μM (rat GAT-1), and 58 μM (rat GAT-2); 119 μM (human GAT-3); 378 μM (rat GAT-3) and 1870 μM (human BGT-3). It is a strong inhibitor of GABA transporters with moderate selectivity for cloned GABA transporters. Guvacine’s affinity (IC50 > 1 mM) for hBGT-1 is low [1]. Guvacine hydrochloride is a strong inhibitor of GABA uptake, although it has little or no effect as a GABA receptor agonist and does not prevent sodium-dependent GABA binding [2]. Guvacine inhibits the absorption of GABA and β-alanine, with IC50s in the cat spinal cord of 23 ± 2 μM and 66 ± 11 μM, respectively, and in the rat cerebral cortex of 8 ± 1 μM and 123 ± 28 μM [3].

Arecaidine and Guvacine, constituents of the nut of Areca catechu, inhibited the uptake of GABA and beta-alanine, but not that of glycine, by slices of cat spinal cord. In cats anesthetised with pentobarbitone, electrophoretic arecaidine enhanced the inhibitory actions of GABA and beta-alanine, but not those of glycine or taurine, on the firing of spinal neurones. Similarly, electrophoretic guvacine enhanced the inhibition of spinal neurones by GABA but not that by glycine. The uptake of GABA by slices of cat cerebellum was inhibited by arecaidine, and the effect of electrophoretic GABA on the firing of cerebellar Purkinje cells was enhanced by electrophoretic arecaidine. When administered intravenously arecaidine failed to affect synaptic inhibitions considered to be mediated by GABA. Intravenous arecaidine had no effect on either spinal prolonged (presynaptic) inhibition (20mg/kg), dorsal root potentials (20mg/kg) or basket cell inhibition of Purkinje cells (250 mg/kg), although topical arecaidine (6.6-10 x 10(-3) M) blocked this latter inhibition. Large doses of arecaidine (1 g/kg subcutaneous) marginally reduced the lethal effects of bicuculline in mice but appeared to have little or no anticonvulsant activity [3].

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Gamma-aminobutyric acid A receptor (GABA(A)R)-mediated postsynaptic currents (IPSCs) were recorded from dopaminergic neurons of the ventral tegmental area of young rats in acute brain slices and from mechanically dissociated neurons. Low concentrations (0.1-0.3 microm) of muscimol, a selective GABA(A)R agonist, increased the amplitude, and reduced the paired pulse ratio of evoked IPSCs. Moreover, muscimol increased the frequency but not the amplitude of spontaneous IPSCs (sIPSCs). These data point to a presynaptic locus of muscimol action. It is interesting that 1 microm muscimol caused an inhibition of sIPSCs, which was reversed to potentiation by the GABA(B) receptor antagonist CGP52432. Isoguvacine, a selective GABA(A)R agonist that belongs to a different class, mimicked the effects of muscimol on sIPSCs: it increased them at low (<or= 0.5=”” microm),=”” and=”” decreased=”” them=”” at=”” a=”” higher=”” concentration=”” (1=”” microm).=”” hence,=”” the=”” activation=”” of=”” presynaptic=”” gaba(a)rs=”” facilitates=”” gaba=”” release,=”” which=”” is=”” limited=”” by=”” gaba(b)rs.=”” furthermore,=”” facilitation=”” sipscs=”” muscimol=”” was=”” eliminated=”” in=”” medium=”” containing=”” tetrodotoxin=”” or=”” cadmium.=”” it=”” noteworthy=”” that=”” sipsc=”” frequency=”” greatly=”” increased=”” 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol(gaboxadol,=”” thip),=”” an=”” agonist=”” with=”” preferential=”” effects=”” on=”” extrasynaptic=”” alpha4betadelta=”” subunits,=”” <strong=””>Guvacine, a GABA transport blocker, which increases ambient GABA levels. In addition, sIPSC frequency was attenuated by furosemide, a selective antagonist of alpha6 subunits. Thus, the presynaptic GABA(A)Rs may be situated at extrasynaptic sites and may contain alpha4/6betadelta subunits. Given the marked sensitivity of extrasynaptic GABA(A)Rs to ambient GABA, alcohols and anaesthetics, these receptors may present a critical site for regulating synaptic function in the developing brain in both physiological and pathological situations [4].</or=>

Most of the chemicals including d(–)-2-amino-5-phospho-pentanoate (AP5), 6,7-dinitroquinoxaline-2,3-dione (DNQX), bicuculline (BIC), cadmium chloride, isoguvacine, furosemide, 4,5,6,7-tetrahydroisoxazolo [5,4-c]pyridine-3-ol (gaboxadol, or THIP), Guvacine hydrochloride, Tyr-D-Ala-Gly-N-Me-Phe-Gly-ol enkephalin (DAMGO) and tetrodotoxin (TTX), Muscimol and CGP52432 were obtained commercially. The solutions, prepared before the experiment, were applied to a dissociated neuron with a Y-tube. This exchanged the external solution surrounding the neurons within 40 ms (Zhou et al. 2006). In experiments on brain slices, chemicals were added in known concentrations to the superfusate. The fact that 10 μm bicuculline blocked most IPSCs (in slices) within 90 s is an indication of the effective bath exchange time. [4]

[1]. Tiagabine, SK&F 89976-A, CI-966, and NNC-711 are selective for the cloned GABA transporter GAT-1. Eur J Pharmacol. 1994 Oct 14;269(2):219-24.

[2]. Structure-activity studies on the inhibition of GABA binding to rat brain membranes by muscimol and related compounds. J Neurochem. 1978 Jun;30(6):1377-82.

[3]. Effects of the Areca nut constituents arecaidine and guvacine on the action of GABA in the cat central nervous system. Brain Res. 1977 Nov 18;136(3):513-22.

[4]. Presynaptic GABAA receptors facilitate GABAergic transmission to dopaminergic neurons in the ventral tegmental area of young rats. J Physiol. 2007 May 1;580(Pt.3):731-43.

Guvacin is an α,β-unsaturated monocarboxylic acid formed by the hydrogenation of nicotinic acid at positions 1-2 and 5-6 of the pyridine ring. It is a plant metabolite and a GABA reuptake inhibitor. It is a β-amino acid, tetrahydropyridine, α,β-unsaturated monocarboxylic acid, pyridine alkaloid, and secondary amino compound. Guvacin is a pyridine alkaloid found in areca nut (also known as betel leaf). It is an experimental drug and currently has no approved indications. Experimental studies are ongoing to determine all physiological effects and mechanisms of action of guvacin. It has been determined that guvacin is a specific GABA reuptake inhibitor with no significant affinity for GABA receptors. Areca nut has been reported to contain guvacin, and relevant data exist. Drug Indications Guvacin currently has no approved indications. Mechanism of Action Experimental studies are ongoing to determine the exact mechanism of action of guvacin. Guvacin is known to selectively bind to presynaptic GABA reuptake transporters, preventing GABA reuptake, but has no affinity for postsynaptic GABA receptors.

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Pharmacodynamics
Experimental studies are still underway to determine all the physiological effects of guvacin.

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Application of the GABA transporter blocker guvacin (20 μm) significantly and reversibly increased the frequency of sIPSCs recorded in brain slices (Figures 7A and C) without inducing significant postsynaptic currents (5 ± 1 pA). Guvacine (20 μm) significantly shifted the cumulative probability map of the interval between consecutive spontaneous inhibitory postsynaptic currents (sIPSC) events to the left (KS test, P < 0.001; Fig. 7B top panel) and increased the sIPSC frequency by 72 ± 14% (n = 7, P = 0.001; Fig. 7B top panel inset), but did not change the amplitude of sIPSC (KS test, P > 0.5; Fig. 7B bottom panel; 0 ± 3%, n = 7, P = 0.46; Fig. 7B bottom panel inset). These results suggest that in the developing brain, elevated levels of environmental GABA can enhance GABAergic sIPSCs through presynaptic mechanisms. [4]

C6H9NO2

127.14116

127.063

C, 56.68; H, 7.14; N, 11.02; O, 25.17

498-96-4

Guvacine hydrochloride;6027-91-4;Guvacine hydrobromide;6027-92-5

3532

Typically exists as solid at room temperature

1.2±0.1 g/cm3

280.8±35.0 °C at 760 mmHg

306 – 309 °C(lit.)

123.6±25.9 °C

0.0±1.2 mmHg at 25°C

1.518

0.72

2

3

1

9

151

0

C1C=C(CNC1)C(=O)O

QTDZOWFRBNTPQR-UHFFFAOYSA-N

InChI=1S/C6H9NO2/c8-6(9)5-2-1-3-7-4-5/h2,7H,1,3-4H2,(H,8,9)

1,2,3,6-tetrahydropyridine-5-carboxylic acid

Guvacine; 498-96-4; 1,2,5,6-tetrahydropyridine-3-carboxylic acid; 1,2,5,6-Tetrahydro-3-pyridinecarboxylic acid; 1,2,5,6-Tetrahydronicotinic acid; CHEBI:5576; GUVACINE [MI]; 41538P325K;

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.)