Differential Transmitter Release from Nerve Terminals Isolated from Basal Ganglia and Substantia Nigra |
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Authors: | J A Hardy J S de Belleroche D Border H F Bradford |
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Institution: | Department of Biochemistry. Imperial College, London, SW7 2AZ, U. K. |
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Abstract: | Abstract: The K+-induced release of amino acids and dopamine from synaptosomes of basal ganglia and substantia nigra of sheep was studied. K+ (56 mM) caused an increase in the release of GABA from caudate, putamen, globus pallidus, and substantia nigra, the increased release being 227, 171, 198, and 366%, respectively, compared with samples incubated without stimulation. The release of glutamate was also increased by 56 mM-K+ (136–183%) from all regions except the globus pallidus, and a significant release of aspartate was only seen in response to K+ stimulation of synaptosomes from putamen (50%). Veratrine (75 μM) also stimulated a similar pattern of amino acid release from these regions. Regional correlation was shown between the presence of an uptake system for an amino acid and its evoked release. 14C]Dopamine formed from L-U-14C]tyrosine was released only from caudate and putamen synaptosomes by K+ stimulation, the increases being 105% and 74%, respectively. Synthesis of 14C]dopamine from L-U-14C]tyrosine occurred only in synaptosomes prepared from these two regions and was not detected in synaptosomes from substantia nigra or globus pallidus although whole-tissue homogenates of substantia nigra were able to synthesise dopamine. |
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