Inhibitory glutamate responses in abdominal muscles of the larval mealworm Tenebrio molitor L. (Coleoptera: Tenebrionidae)
Japanese Journal of Applied Entomology and Zoology 46(3): 153-158
To study the inhibitory mechanisms of the ventral longitudinal muscle fibers of the mealworm larva Tenebrio molitor, the effects of several inhibitory compounds on the excitatory post-synaptic potentials (EPSPs), membrane potentials and L-glutamate-induced potentials (GLU-Ps) were investigated by means of a microelectrode. Application of GABA, glycine, L-[alpha]-alanine, [beta]-alanine, taurine and picrotoxin were used in the muscle preparations. None of these compounds had an effect on the EPSP and membrane potentials. In contrast, GLU-Ps were potentiated by picrotoxin, GABAA antagonist and chloride channel blocker, whereas GABA, glycine, L-[alpha]-alanine, [beta]-alanine and taurine had no effect. This potentiation of GLU-Ps may result from a blockade of glutamate-gated chloride channels by picrotoxin. These results suggested the presence of extrajunctional chloride-channel-type glutamate receptors in the ventral longitudinal muscle fibers of the larval mealworm. A similar result was obtained with a glutamate agonist, quisqualate, suggesting the chloride channel may be under the control of a quisqualate like receptor.