Method of screening binding of a compound to a receptor

1. A method of measuring affinity of a test compound for a receptor protein, the method comprising:

(a) providing a receptor-test compound complex comprising a non-NMDA glutamate receptor and a test compound bound thereto; then

(b) contacting the receptor-test compound complex of step (a) with a known concentration of quinoxaline derivative selected from the group consisting of a compound of Formula I:

 wherein R 1 and R 2 are independently selected from the group consisting of hydrogen; halo, substituted or unsubstituted alkyl, alkenyl, alkynyl; substituted or unsubstituted heteroalkyl; acyl; and substituted or unsubstituted aryl; and

R 3 and R 4 are independently selected from the group consisting of hydrogen, hydroxy, halo; substituted or unsubstituted alkyl, alkenyl, alkynyl; substituted or unsubstituted heteroalkyl; acyl, carboxy, cyano, cyanoalkyl, nitro, amino, sulfonyl, alkylsulfonyl, amido, and sulfonamido;

under conditions wherein the quinoxaline derivative binds to the receptor, thereby yielding a receptor-quinoxaline complex and an amount of free quinoxaline derivative; and then

(c) measuring the amount of the free quinoxaline derivative generated as a result of step (b), using visible absorption spectrophotometry, and comparing the amount of the free quinoxline to the known concentration of quinoxaline used in step (b), whereby the affinity of the test compound for the receptor is determined.

2. The method of claim 1 , wherein a visible spectrum is taken at wavelengths ranging from about 315 to about 450 mu.

3. The method of claim 1 , further comprising generating a control visible spectrum comprising a difference spectrum between a visible spectrum of the quinoxaline derivative ligand in the absence of the receptor and a visible spectrum of the quinoxaline derivative ligand bound to the receptor.

4. A method of measuring affinity of a test compound for a non-NMDA glutamate receptor protein, the method comprising:

(a) contacting a non-NMDA glutamate receptor with a known amount of a quinoxaline derivative under conditions wherein at least a portion of the quinoxaline derivative binds to the receptor, thereby yielding a receptor-quinoxaline complex and a first amount of free quinoxline derivative; then

(b) recording a visible spectrum of the free quinoxline from step (a); then

(c) contacting the complex of step (a) with a test compound under conditions and for a time sufficient to allow the test compound to bind to the receptor, thereby displacing at least a portion of the quinoxaline derivative from the complex and yielding a receptor-test compound complex and a second amount of free quinoxaline derivative;

(d) recording a visible spectrum of the free quinoxline derivative from step (c); and then

(e) comparing the spectrum from step (b) wit the spectrum from step (d), whereby the affinity of the test compound for the receptor is determined.

5. The method of claim 4 , wherein in step (a) the non-NMDA glutamate receptor is contacted with a quinoxaline derivative selected from the group consisting of a compound of Formula I:

wherein R 1 and R 2 are independently selected from the group consisting of hydrogen; halo, substituted or unsubstituted alkyl, alkenyl, alkynyl; substituted or unsubstituted heteroalkyl; acyl; and substituted or unsubstituted aryl; and

R 3 and R 4 are independently selected from the group consisting of hydrogen, hydroxy, halo; substituted or unsubstituted alkyl, alkenyl, ailcynyl; substituted or unsubstituted heteroalkyl; acyl, carboxy, cyano, cyanoalkyl, nitro, amino, sulfonyl, alkylsulfonyl, amido, and sulfonamido.

6. The method of claim 5 , wherein R 1 and R 2 of the quinoxline derivative are hydrogen.

7. The method of claim 5 , wherein the quinoxline derivative is selected from the group consisting of 6-cyano-7-nitro-2,3-dihydroxyquinoxaline; 6,7-dinitro-2,3-dihydroxyquinoxaline; and 6-nitro-2,3-dihydroxyquinoxaline-7-sulfonamide.