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Selectivity of the uptake of glutamate and GABA in two morphologically distinct insect neuromuscular synapses

1985; Elsevier BV; Volume: 348; Issue: 1 Linguagem: Inglês

10.1016/0006-8993(85)90365-8

1872-6240

Jan van Marle, T. Piek, Th. Lammertse, A. Lind, J. van Weeren‐Kramer,

Insect and Arachnid Ecology and Behavior

The common inhibitor (CI) and slow excitor tibiae (SETi) innervated slow muscles 135cd of the locust Schistocera gregaria were incubated under high-affinity uptake conditions either in [3H]GABA or in [3H]glutamate. [3H]GABA is accumulated in the glia of the nerve endings of the CI as well as the SETi; however, it is accumulated only in the terminal axons of the CI, not in the terminal axons of the SETi. The grain densities above the glia and above the CI terminal axons are approximately 2 grains/μm2. After incubation in [3H]glutamate the grain densities above the CI terminal axons and the SETi terminal axons are approximately 4 grains/μm2; the grain densities above the glia of both types of nerve endings are approximately 17 grains/μm2. The relatively high labeling (3 grains/μm2) of the muscles after incubation in the presence of glutamate is ascribed to the high metabolic requirements of slow muscles. The conclusion is drawn that a high-affinity uptake system for GABA is present in the CI terminal axons and in the glia of both the CI and SETi nerve endings. However, while the glutamate uptake in the CI and SETi nerve endings of the slow 1 35cd is comparable to the high-affinity uptake of glutamate in the fast excitor tibiae (FETi) nerve endings of the fast retractor unguis muscle, a high-affinity uptake of glutamate was only demonstrated in the glia of both types of nerve endings. A high-affinity uptake in the terminal axons of the CI and SETi may be masked by an extensively low-affinity uptake of glutamate by the muscles.