GABAA receptors (GABAARs); glycine receptors (GlyRs)
Picrotonin targets glycine receptors (GlyRs), specifically blocking α2 GlyR, α1 GlyR, and α3 GlyR. As a component of picrotoxin, it also contributes to the antagonism of GABAA receptors (GABAARs). Glycine receptors are ligand-gated chloride channels that mediate inhibitory neurotransmission in the central nervous system. By blocking these receptors, picrotonin inhibits chloride influx and reduces inhibitory neurotransmission. Its effects on GABAARs and GlyRs make it a valuable tool for studying inhibitory neurotransmission and the role of these receptors in neurological function.

Picrotin has an IC50 value of 13.1 μM and is sensitive to α2 GlyR[1].Picrotoxin, an antagonist of structurally-rated GABA(A) receptors (GABA(A)Rs) and glycine receptors (GlyRs), is an equimolar mixture of picrotoxinin (PTXININ) and picrotin (PTN). These compounds share a common structure except that PTN contains a slightly larger dimethylmethanol in place of the PTXININ isopropenyl group. Although the homomeric alpha1 GlyR is equally sensitive to both compounds, we show here that homomeric alpha2 and alpha3 GlyRs, like most GABA(A)Rs, are selectively inhibited by PTXININ. As conservative mutations to pore-lining 6' threonines equally affect the sensitivity of the alpha1 GlyR to both compounds, we conclude that PTXININ and PTN bind to 6' threonines by hydrogen bonding with exocyclic oxygens common to both molecules. In contrast, substitution of the 2' pore-lining glycine by serine selectively reduces PTN sensitivity, whereas the introduction of 2' alanines selectively increases PTXININ sensitivity. These results define the orientation of PTXININ and PTN binding in the alpha1 GlyR pore and allow us to conclude that the relatively reduced sensitivity of PTN at GABA(A)Rs and alpha2 and alpha3 GlyRs is due predominantly to its larger size and reduced ability to form hydrophobic interactions with 2' alanines.[1]
In vitro, Picrotonin has been characterized as an inhibitor of glycine receptors (GlyRs) which blocks α2 GlyR, α1 GlyR, and α3 GlyR. As a component of picrotoxin, it also contributes to the antagonism of GABAA receptors. Its effects on these receptors are typically assessed using electrophysiological techniques such as patch-clamp recording in cells expressing the receptors. These in vitro activities confirm its potential for studying inhibitory neurotransmission and receptor pharmacology.

In vivo, Picrotonin is used as a component of picrotoxin to study GABA and glycine receptor function. Picrotoxin is a well-known convulsant that induces seizures by blocking inhibitory neurotransmission. However, detailed in vivo efficacy and safety data for Picrotonin specifically are described in the primary literature. The compound is primarily used in research applications and is not intended for human therapeutic use. Its convulsant activity makes it a valuable tool for studying epilepsy and seizure mechanisms.

Contrary to its effect on the gamma-aminobutyric acid type A and C receptors, picrotoxin antagonism of the alpha1 homomeric glycine receptors (GlyRs) has been shown to be non-use-dependent and nonselective between the picrotoxin components picrotoxinin and picrotin. Picrotoxin antagonism of the embryonic alpha2 homomeric GlyR is known to be use-dependent and reflects a channel-blocking mechanism, but the selectivity of picrotoxin antagonism of the embryonic alpha2 homomeric GlyRs between picrotoxinin and picrotin is unknown. Hence, we used the patch clamp recording technique in the outside-out configuration to investigate, at the single channel level, the mechanism of picrotin- and picrotoxinin-induced inhibition of currents, which were evoked by the activation of alpha2 homomeric GlyRs stably transfected into Chinese hamster ovary cells. Although both picrotoxinin and picrotin inhibited glycine-evoked outside-out currents, picrotin had a 30 times higher IC50 than picrotoxinin. Picrotin-evoked inhibition displayed voltage dependence, whereas picrotoxinin did not. Picrotoxinin and picrotin decreased the mean open time of the channel in a concentration-dependent manner, indicating that these picrotoxin components can bind to the receptor in its open state. When picrotin and glycine were co-applied, a large rebound current was observed at the end of the application. This rebound current was considerably smaller when picrotoxinin and glycine were co-applied. Both picrotin and picrotoxinin were unable to bind to the unbound conformation of the receptor, but both could be trapped at their binding site when the channel closed during glycine dissociation. Our data indicate that picrotoxinin and picrotin are not equivalent in blocking alpha2 homomeric GlyR.[2]
For in vitro biochemical assays, Picrotonin is evaluated for its effects on glycine and GABA receptors. Receptor binding assays can be performed using radioligand competition binding with membrane preparations from cells expressing the receptors. Electrophysiological assays using patch-clamp or two-electrode voltage clamp in Xenopus oocytes or mammalian cells expressing GlyRs or GABAARs are used to measure receptor inhibition. IC50 values for receptor blockade are determined from dose-response curves. These cell-free and cell-based assays help characterize the compound's receptor blocking activity.

In vitro cellular assays for Picrotonin are performed using cells expressing glycine or GABA receptors. Cells are cultured in standard media and treated with the compound at various concentrations. Receptor function is assessed using electrophysiological techniques or fluorescence-based membrane potential assays. Receptor binding is assessed using radioligand binding assays. These cellular assays help validate the compound's receptor blocking activity and characterize its potency and selectivity.

In vivo animal experiments with Picrotonin are typically conducted using picrotoxin, which contains picrotonin as a component. Picrotoxin is administered via intraperitoneal injection or intracerebroventricular injection to induce seizures in animal models. Seizure activity is monitored by behavioral observation or electroencephalography (EEG). These studies are used to investigate seizure mechanisms and to test anticonvulsant drugs. Researchers should consult the primary literature for detailed protocols.

Pharmacokinetic properties of Picrotonin are not extensively documented. As a small molecule with a molecular weight of 310.30, it is expected to have moderate bioavailability. The compound is soluble in organic solvents. Detailed PK parameters such as half-life, Cmax, Tmax, AUC, and protein binding are not available in the literature. The compound should be stored under recommended conditions to maintain stability.

The intraperitoneal LD50 in mice was 135 mg/kg. (Journal of Medicinal Chemistry, 11(729), 1968)
The toxicological profile of Picrotonin is related to its mechanism of action as a glycine and GABA receptor antagonist. By blocking inhibitory neurotransmission, it can induce seizures and convulsions. The compound is intended for research use only and not for human therapeutic applications. Appropriate safety precautions should be followed when handling this compound due to its convulsant activity. Comprehensive toxicity studies have been conducted in the context of picrotoxin research.

[1]. A proposed structural basis for picrotoxinin and picrotin binding in the glycine receptor pore. J Neurochem. 2007 Oct;103(2):580-9.

[2]. Mechanisms for picrotoxinin and picrotin blocks of alpha2 homomeric glycine receptors. J Biol Chem. 2007 Jun 1;282(22):16016-35.

Picrotin is an organic heteropentacyclic compound, a derivative of Picrotin toxin, whose olefinic double bond undergoes hydration to form the corresponding tertiary alcohol. It is the less toxic component of Picrotin toxin and lacks GABA activity. It is a plant metabolite. Picrotin is an organic heteropentacyclic compound with structural features of epoxides, tertiary alcohols, γ-lactones, diols, and Picrotin sesquiterpenes. Functionally, it is related to Picrotin toxin. Picrotin has been reported to exist in Dendrobium moniliforme and Anamirta cocculus, with relevant data available. See also: Picrotin toxin (note moved here).
Picrotonin is a valuable research tool for studying glycine and GABA receptor function. As a component of picrotoxin, it is used to investigate inhibitory neurotransmission, seizure mechanisms, and the pharmacology of GlyRs and GABAARs. Its ability to block multiple GlyR subtypes (α1, α2, α3) makes it useful for studying the role of different GlyR subtypes in neurological function. The compound can be employed in drug discovery research to identify new modulators of inhibitory neurotransmission and to develop new treatments for epilepsy and other neurological disorders.

C15H18O7

310.29922

310.105

C, 58.06; H, 5.85; O, 36.09

21416-53-5

442291

White to off-white solid powder

1.59g/cm3

595.8ºC at 760 mmHg

256-258ºC

228.9ºC

1.12E-16mmHg at 25°C

1.637

-0.8

2

7

1

22

644

8

CC([C@@H]1[C@H]2OC(=O)[C@@H]1[C@@]1(C[C@H]3O[C@@]43C(O[C@H]2[C@]14C)=O)O)(C)O

RYEFFICCPKWYML-QCGISDTRSA-N

InChI=1S/C15H18O7/c1-12(2,18)6-7-10(16)20-8(6)9-13(3)14(7,19)4-5-15(13,22-5)11(17)21-9/h5-9,18-19H,4H2,1-3H3/t5-,6+,7-,8-,9-,13-,14-,15+/m1/s1

(1R,3R,5S,8S,9R,12S,13R,14S)-1-hydroxy-14-(2-hydroxypropan-2-yl)-13-methyl-4,7,10-trioxapentacyclo[6.4.1.19,12.03,5.05,13]tetradecane-6,11-dione

Picrotin; NSC-129536; NSC 129536; picrotin; 21416-53-5; Picrotin (VAN); CHEBI:8205; U06Z6QD7N2; PICROTIN [MI]; DSSTox_CID_25605; DSSTox_RID_80998; NSC129536

2934.99.03.00

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)

DMSO : ~100 mg/mL (~322.27 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (8.06 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (8.06 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
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.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (8.06 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), suspension solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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