The methods of the present invention allow the screening of a test composition for non-receptor-specific GPCR desensitization inhibitory activity. The methods involve screening a test composition for an indication of GPCR desensitization inhibitory activity against two or more GPCRs that are different from each other. When there is an indication that a particular test composition has GPCR desensitization inhibitory activity with respect to each of the two or more GPCRs that are different from one another, then, according to the present invention, there is an indication that the test composition has non-receptor-specific GPCR desensitization inhibitory activity.