Effect of denervation and local damage on extrajunctional L-glutamate receptors in locust muscle

Abstract

EXTRAJUNCTIONAL receptors occur in both normal vertebrate muscle¹ and locust muscle² as demonstrated by iontophoretically applied acetylcholine (ACh) and L-glutamate respectively. Two types of extrajunctional glutamate receptors occur in locust muscle in addition to the junctional receptors³. The biphasic response (depolarisation preceding hyperpolarisation) seen when glutamate is applied iontophoretically to extrajunctional regions of locust muscle results from simultaneous activation of the two types of extrajunctional glutamate receptors³. The D receptor (which mediates a depolarisation) is activated by L-glutamate but insensitive to the glutamate analogue DL-ibotenate, while the H receptor (which mediates a hyperpolarisation) is activated by both L-glutamate and DL-ibotenate. This pharmacological difference has allowed separate investigation of the two types of receptors.