DEVELOPMENT OF MUSCARINIC M(3) AND M(4) RECEPTOR ANTIBODIES WITH PHARMACOLOGICAL ACTIVITIES

AIM: To investigate the feasibility of developing subtype-selective an ti-receptor antibodies with pharmacological activities for the study o f subtypes of receptors. METHODS: New Zealand white rabbits were immun ized with synthesized subtype-selective peptide segments of m(3) and m (4) receptors to develop antibodies. The effects of the antibodies on ligand-binding to muscarinic receptors were studied by competitive rad ioligand assay. The effects of the prepared antibodies on the contract ion or relaxation activity of ACh in isolated rat ilea and aortic ring s were studied. RESULTS: Antibodies against synthesized m(3) and m(4) receptor subtype-selective peptides were successfully prepared. Both a ntibodies inhibited [H-3]QNB binding to muscarinic receptors with diff erent maximal inhibitions which may be the proportions of m(3) or m(4) subtypes among the total muscarinic receptors in the tissues. The max imal inhibitory rates in rat cerebral cortex, myocardium, and salivary glands were 12.1% +/- 2.1%, 15.7% +/- 1.1%, and 63.6% +/- 2.8% for m3 antibodies,whereas 28% +/- 6%, 19.3% +/- 2.6%, and 1.6% +/- 1.4% for m(4) antibodies respectively. The m(3) antibodies inhibited the contra ction activity of ACh in isolated rat ilea and the relaxation activity of ACh in isolated rat aortic rings. CONCLUSION: It is feasible to de velop subtype-selective anti-receptor antibodies as new tools in the s tudy of the functions of m(3) and m(4) subtypes of muscarinic receptor s.