X.: Organophosphate and carbamate compounds have pre- and postjunctional effects at the insect glutamatergic synapse

The effects of the organophosphate compounds diisopropylfluo-rophosphate (DFP), dimethylphosphoramidocyanidic acid ethyl ester (tabun), 0-ethyl S-2 diisopropylaminoethyl-methyl phos-phonothiolate (VX) and the carbamate compound 1,2,3,3a,8,8a-hexahydro-1,3a,8-tnmethylpyrrolo[2,3-b]indol-5-ol methylcarba-mate (physostigmine) were studied on the metathoracic flexor and extensor tibialis muscles of Locusta migratoria. These anti-cholinesterase (anti-ChE) agents interacted with pre- and post-synaptic regions of the glutamatergic neuromuscular synapse. In physiological solution, containing normal calcium concentra-tion (2 mM), these agents initiated spontaneous excitatory post-synaptic potentials (EPSP5) and muscle action potentials (AP5) alternating with periods of reduced spontaneous activity in which only miniature excitatory postsynaptic potentials (MEPSPs) coul