A technique for the determination of the production and degradation rates of mouse brain M-receptors was established. The selective alkylating ager.t BCM was given in vivo to irreversibly inhibit the M-receptors and the 3H-QNB binding assay was used to monitor the time-related increase of newly synthesized receptors. A tracer kinetics mathematical model was used to calculate the parameters. The results of three separate experiments with Balb-C mice were close to each other

the average production rate being 37.34fmol/mg protein/h

the average degradation rate constant being 0.035/h

and the half-time being 19.82h. The significance of this technique in the study of the mechanism of pathological changes in brain M-receptors and drug actions was discussed.