Metabotropic glutamate receptors (mGluR)

In isolated rod bipolar cells, DL-AP4 (500 μM) decreases tonic inward currents by blocking ion channels at a holding potential of -33 mV [1]. DL-AP4 (0.1 M; 1h) inhibits glutamate's excitatory effects by acting through iontophoresis on receptors on the locust sarcolemma [2]. With an apparent Kd of 2.5 μM, compound 2, DL-AP4, antagonizes excitatory synapses in the lateral penetrating pathway of rat hippocampus slices [3]. The photoresponse of a series of 10 ms 405 nm flashes at the following intensities is blocked by DL-AP4 (50 µM; 0–2 seconds): 3, 10, 30, 100, 300, 990, 3000, and 9900 photons µm-2[4].

Four experiments were performed to assess the effects of ON channel blockade with the glutamate analog 2-amino-4-phosphonobutyrate (APB) on brightness and contrast perception in monkeys. In Experiment 1, we demonstrate that stimuli brighter than background (incremental stimuli) appear less bright following ON channel blockade. This decrease in brightness is not enough to account for the previously observed threshold increase for detection of incremental stimuli following APB administration (Schiller et al., 1986; Dolan & Schiller, 1989). Experiment 2 examines the role of the ON and OFF channels in the interaction between local contrast and apparent brightness. The phenomenon of simultaneous contrast was examined under normal conditions and following APB administration. We find that even following ON channel blockade, the brightness of a stimulus is determined primarily by its contrast with its immediate background. This indicates that the lateral processes involved in simultaneous contrast can operate even when one channel has been compromised. In Experiment 3, we examined the role of the ON channel in detection of stimuli that appear by virtue of changes in background vs. foreground luminance. We find that the ON channel selectively conveys information pertaining not only to the temporal nature that defines the stimulus as incremental but also to the spatial features that define it as incremental. In Experiment 4, we test the hypothesis that incremental and decremental temporal luminance ramps are differentially processed by the ON and OFF channels to a higher degree than are step-luminance changes. We find that the detection of incremental ramps is no more affected than is the detection of incremental steps following APB administration. [https://pubmed.ncbi.nlm.nih.gov/8011580/]

The intraperitoneal LD50 in mice was 880 mg/kg. Behavioral studies: changes in kinesiological activity (specific assay). Polish Journal of Pharmacology and Pharmaceutical Sciences, 37(575), 1985.

[1]. 2-Amino-4-phosphonobutyric acid as a glutamate antagonist on locust muscle. Nature. 1976 Jul 29;262(5567):408-9.
[2]. Responses of rod bipolar cells isolated from the rat retina to the glutamate agonist 2-amino-4-phosphonobutyric acid (APB). J Neurosci. 1991 Aug;11(8):2372-82.
[3]. Cyclic analogues of 2-amino-4-phosphonobutanoic acid (APB) and their inhibition of hippocampal excitatory transmission and displacement of [3H]APB binding. J Med Chem. 1986 Oct;29(10):1988-95.
[4]. Separate ON and OFF pathways in vertebrate vision first arose during the Cambrian. Curr Biol. 2020 Jun 8;30(11):R633-R634.

Rod bipolar cells were isolated from the retinas of adult rats using enzymatic digestion (papain) and mechanical separation. Almost all intact bipolar cells in the isolates expressed protein kinase C (PKC), an immunoreactive protein kinase, a selective marker for rod bipolar cells in the in vivo retina. Whole-cell recording was performed using a patch-clamp electrode containing nystatin to minimize the elution of cytoplasmic components required to maintain ion currents. A sustained inward current was observed at a clamping potential of -33 mV. This current was reduced by the glutamate agonist 2-amino-4-phosphonate butyrate (APB) by closing ion channels. Under normal conditions, Na+ appears to be the predominant charge carrier. Both intracellular and extracellular Ca2+ concentrations significantly affected the APB-sensitive current. We conclude that in situ rod bipolar cells are in a depolarized state at the onset of light exposure. [2] We prepared conformationally restricted analogs of 2-amino-4-phosphonobutyric acid (APB, 2), wherein the structure of APB was incorporated into a cyclopentane (3) or cyclohexane (4) ring. The desired analogs were obtained by hydrophosphonylation of the corresponding cycloenone followed by Strecker amino acid synthesis. The relative configurations of 3a (trans), 3b (cis), 4a (cis), and 4b (trans) were determined by 13C NMR studies. Compounds 3b, 4a, and 4b showed low activity as inhibitors of excitatory synaptic field potentials in the rat hippocampal perforation pathway. Analogs 4a and 4b also showed little activity in displacing [3H]APB from the synaptic membrane. On the other hand, cyclopentyl APB analog 36 exhibited a strong inhibitory effect on the binding of [3H]APB, with an IC50 value of 4.7 μM. This further confirms that the APB binding site in the rat brain synaptosome membrane preparation is not the same site as the receptor mediating APB-induced inhibition of the lateral perforation pathway. Among the four cyclic APB analogs, 3a has the most similar bioactivity spectrum to APB. It showed significant inhibitory activity against the projection of the lateral entorhinal cortex to hippocampal granule cells (IC50 value of 130 μM). Similar to APB, 3a also showed selectivity for the lateral perforation pathway rather than the medial perforation pathway. Its activity in the radioligand binding assay was consistent with its activity against the lateral perforation pathway. Therefore, 3a appears to be the closest to the active conformation of mimicking APB, suggesting that a cis-folded conformation of the amino and phosphonate moieties may approximate the active conformation of APB. [3] Ellis et al. found that novel metabolized glutamate receptors on retinal ON and OFF bipolar cells and on the dendrites of ON bipolar cells were present in lampreys. They concluded that the basic organizational principles of independent ON and OFF pathways first appeared in the visual system of vertebrates in the Late Cambrian period more than 500 million years ago. [4]

C4H10NO5P

183.099662303925

183.03

C, 26.24; H, 5.51; N, 7.65; O, 43.69; P, 16.92

6323-99-5

1263093-79-3

2207

White to off-white solid powder

-5.5

4

6

4

11

187

0

C(CP(=O)(O)O)C(C(=O)O)N

DDOQBQRIEWHWBT-UHFFFAOYSA-N

InChI=1S/C4H10NO5P/c5-3(4(6)7)1-2-11(8,9)10/h3H,1-2,5H2,(H,6,7)(H2,8,9,10)

2-amino-4-phosphonobutanoic acid

6323-99-5; 2-amino-4-phosphonobutanoic acid; 2-Amino-4-phosphonobutyric acid; DL-AP4; 20263-07-4; DL-2-Amino-4-phosphonobutyric acid; Butanoic acid, 2-amino-4-phosphono-; (+/-)-2-Amino-4-phosphonobutyric acid;

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.)