Developmental loss of a smooth muscle muscarinic receptor population.

The radioligand [3H]quinuclidinyl benzilate has been used to examine the muscarinic receptor population of the chick expansor secundariorum muscle during its post-hatch development. At hatch the muscle bound 0.165 fmol of the ligand, but during the following two weeks binding decreased rapidly. Further reduction in ligand binding to the adult stage was observed, but at a much slower rate. The developmental loss of binding sites within this tissue corresponds to previously demonstrated reduction in acetylcholine sensitivity.