Pharmacologically separable [(3)H]glutamate binding sites on insect muscle membranes.

A high affinity, saturable, [(3)H]l-glutamate binding site has been described in a cockroach (Periplaneta americana) coxal muscle membrane preparation. This site exhibits a K(D) of 1.1 ?M and a B(max) of 15.5 pmol mg(?1) protein. The pharmacological profile is compatible with that expected of a functional l-glutamate receptor and there is good agreement with physiological data obtained for the insect neuromuscular junction in other laboratories. There appear to be at least two subpopulations of l-glutamate binding sites in cockroach muscle membranes which can be distinguished biochemically with the agonists ibotenate and quisqualate.