Preferential release of newly synthesized [3H]GABA from striatal slices to preloaded [3H]GABA |
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Authors: | Yukio Yoneda Kouji Kanmori Mamoru Takahashi Ping-Ping Zuo In-Ho Paik Kinya Kuriyama |
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Institution: | Department of Pharmacology, Kyoto Prefectural University of Medicine, Kamikyo-Ku, Kyoto Japan |
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Abstract: | The release of 3H]GABA which is newly synthesized from 3H]l-glutamic acid (GLU) has been examined using striatal slices obtained from the rat brain. It was found that 8–10% of 3H]GLU transported was converted to 3H]GABA during the incubation of striatal slices in the presence of nipecotic acid (5 × 10?5 M). Nipecotic acid was added to the medium in order to prevent possible reuptake of 3H]GABA released during its synthesis, and it was found to have no significant effect on the formation of 3H]GABA from 3H]GLU as well as on the uptake of 3H]GLU. The application of high potassium (60 mM) stimulation exhibited a significant enhancement of the release of this newly synthesized 3H]GABA in a Ca2+ dependent manner. Kinetic analysis revealed that the evoked release of newly synthesized 3H]GABA was approximately two times greater than that of previously-loaded 3H]GABA, whereas no significant difference was observed in the spontaneous release. An immobilization stress in water failed to affect the release of newly synthesized 3H]GABA from striatal slices despite the occurrence of a significant enhancement of GABA formation in this structure.These results suggest that newly synthesized GABA may be preferentially released from its nerve terminals in response to the excitation of neurons at least in the striatum as compared with previously accumulated GABA. |
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Keywords: | To whom correspondence should be addressed |
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