Glutamate uptake after stimulation-induced depletion of vesicle numbers in neuromuscular junctions of Locusta migratoria L

The uptake and metabolism of L-glutamate by tissue slices of the cestode Hymenolepis diminuta

The in vitro uptake of L-[3H]glutamate by tissue slices of the cestode Hymenolepis diminuta, denuded of tegument, was investigated. Two sodium concentration-dependent mechanisms, one of high affinity (Kt 1.8 X 10(-5) M; Vmax 4.76 pMoles/min/mg wet weight) and another of low affinity (Kt 2.2 X 10(-4) M; Vmax 50.7 pMoles/min/mg wet weight), were identified, in addition to a sodium insensitive component. Exchange of preloaded [3H]glutamate did not occur in tissue slices incubated in dilute unlabelled glutamate. Acidic amino acids, imipramine and fluoxetine were effective inhibitors of high and low affinity uptake, while glutamate receptor ligands, neurotransmitters and some antihelminthics generally were not. The concentrations present in, and the metabolism of glutamate by, tissue slices was examined by HPLC. The significance of the three modes of glutamate uptake and their possible role in the physiology of H. diminuta are discussed.

The uptake and release of glutamate at the crayfish neuromuscular junction

The abdominal slow flexor muscle of the crayfish (Cambarus clarkii) was pre-incubated in deuterium-labelled glutamate (glutamate-d5) solution, and the release of glutamate, glutamate-d5 and aspartate in the bath solution was measured by mass fragmentography. The glutamate-d5 was taken up into the preparation and released together with endogenous glutamate. The resting release of glutamate-d5 was 8.2 +/- 0.96 pmol/10 min after the incubation with 0.5 mM-glutamate-d5, and those of endogenous glutamate and aspartate were 7.4 +/- 1.19 and 2.8 +/- 0.81 pmol/10 min, respectively. The release of glutamate-d5 was not significantly increased by nerve stimulation, while that of endogenous glutamate was increased by about 9.7 pmol/10 min above the resting release. The application of high-K solution induced a net increase of 1.9 pmol/10 min in glutamate-d5 release, 6.1 pmol/10 min in endogenous glutamate release and 7.9 pmol/10 min in aspartate release. The relative amount of glutamate-d5 accumulated into the preparation during pre-incubation with 0.5 mM-glutamate-d5 was a few per cent of the endogenous glutamate in the preparation. It is concluded that the exogenous glutamate is taken up mainly into a compartment which differs from that related to nerve evoked transmitter release and that high-K solution has effects on the amino acid release which differ from those of nerve stimulation.

Inhibition of the glutamate uptake in the excitatory neuromuscular synapse of the locust by delta-philanthotoxin; a component of the venom of the solitary wasp Philanthus triangulum F. A high resolution autoradiographic study

Glutamate uptake in insect neuromuscular junctions is inhibited by delta-philanthotoxin. Two other components of the philanthus venom (beta- and gamma-philanthotoxin) do not affect this glutamate uptake. No synergism between the active delta-philanthotoxin and the two inactive components had to be assumed to explain the inhibition by the Philanthus venom.