MSX-2 is a selective

adenosine Adenosine (symbol A) is an organic compound that occurs widely in nature in the form of diverse derivatives. The molecule consists of an adenine attached to a ribose via a β-N9-glycosidic bond. Adenosine is one of the four nucleoside buildin ...

A_2A receptor antagonist used in

scientific research The scientific method is an empirical method for acquiring knowledge that has characterized the development of science since at least the 17th century (with notable practitioners in previous centuries; see the article history of scientific ...

. It is a

xanthine Xanthine ( or ; archaically xanthic acid; systematic name 3,7-dihydropurine-2,6-dione) is a purine base found in most human body tissues and fluids, as well as in other organisms. Several stimulants are derived from xanthine, including caffeine, ...

and a

derivative In mathematics, the derivative of a function of a real variable measures the sensitivity to change of the function value (output value) with respect to a change in its argument (input value). Derivatives are a fundamental tool of calculus. ...

of the

non-selective In biochemistry and pharmacology, a ligand is a substance that forms a complex with a biomolecule to serve a biological purpose. The etymology stems from ''ligare'', which means 'to bind'. In protein-ligand binding, the ligand is usually a mol ...

adenosine receptor antagonist An adenosine receptor antagonist is a drug which acts as an antagonist of one or more of the adenosine receptors. The best known are xanthines and their derivatives (natural: caffeine, theophylline, and theobromine; and synthetic: PSB-1901), but t ...

caffeine Caffeine is a central nervous system (CNS) stimulant of the methylxanthine class. It is mainly used recreationally as a cognitive enhancer, increasing alertness and attentional performance. Caffeine acts by blocking binding of adenosine t ...

. The

affinities In post-classical history, an affinity was a collective name for the group ( retinue) of (usually) men whom a lord gathered around himself in his service; it has been described by one modern historian as "the servants, retainers, and other foll ...

(K_i) of MSX-2 for the human

adenosine receptor The adenosine receptors (or P1 receptors) are a class of purinergic G protein-coupled receptors with adenosine as the endogenous ligand. There are four known types of adenosine receptors in humans: A1, A2A, A2B and A3; each is encoded by a dif ...

s are 5.38 to 14.5nM for the adenosine A_2A receptor, 2,500nM for the adenosine A₁ receptor (172- to 465-fold lower than for the A_2A receptor), and >10,000nM for the adenosine A_2B and A₃ receptors (>690-fold lower than for the A_2A receptor). MSX-2 has poor

water solubility An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would be re ...

, which has limited the use of MSX-2 itself. Water-soluble

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ...

prodrugs of MSX-2, including

MSX-3 MSX-3 is a binding selectivity, selective adenosine adenosine A2A receptor, A2A receptor adenosine receptor antagonist, antagonist used in scientific research. Similarly to MSX-4, it is a water solubility, water-soluble ester prodrug of MSX-2. ...

phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phosph ...

ester prodrug) and

MSX-4 MSX-4 is a selective adenosine A2A receptor antagonist used in scientific research. It is a water-soluble amino acid ester prodrug of MSX-2, the active metabolite of the drug. MSX-4 reverses the motivational deficits induced by the dopamin ...

(an

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha ...

ester prodrug), have been developed and used in place of MSX-2. MSX-3 is best-suited for use by

intravenous administration Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutrie ...

, whereas MSX-4 can be administered by

oral administration Oral administration is a route of administration where a substance is taken through the mouth. Per os abbreviated to P.O. is sometimes used as a direction for medication to be taken orally. Many medications are taken orally because they are in ...

. MSX-3 and MSX-4 reverse motivational deficits in animals and hence have the capacity to produce pro-motivational effects. MSX-2 and MSX-3 were first described in the

scientific literature : ''For a broader class of literature, see Academic publishing.'' Scientific literature comprises scholarly publications that report original empirical and theoretical work in the natural and social sciences. Within an academic field, sci ...

by 1998. Subsequently, MSX-4 was developed and described by 2008.

References

3-Methoxyphenyl compounds Adenosine receptor antagonists Experimental drugs Pro-motivational agents Prodrugs Propargyl compounds Xanthines {{Pharma-stub

See also

References