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.