Increase in Striatal [3H]Muscimol Binding Following Intrastriatal Injection of Kainic Acid: A Denervation Supersensitivity Phenomenon |
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Authors: | Kinya Kuriyama Etsuo Kurihara Yoshihisa Ito Yukio Yoneda |
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Institution: | Department of Pharmacology, Kyoto Prefectural University of Medicine, Kamikyo-ku, Kyoto 602, Japan |
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Abstract: | The effect of intrastriatal microinjection of kainic acid (KA) on specific binding of 3H]muscimol to the particulate fractions obtained from corpus striatum (CS), globus pallidus (GP), substantia nigra (SN), and cerebral cortex (CC) was examined. Seven days after the unilateral intrastriatal microinjection of KA, the amount of specifically bound 3H]muscimol was significantly increased at the injected site, whereas no significant alteration of 3H]muscimol binding was found in GP, SN, or CC. Scatchard analysis of striatal binding revealed that microinjection of KA significantly increased the affinity (KD) of GABA receptors on the injected (lesioned) side of the CS without affecting the total number of binding sites (Bmax) therein. This significant increase in 3H]muscimol binding, however, was eliminated by pretreating particulate fractions from the CS with Triton X-100, a non-ionic detergent. No statistically significant difference in amounts of 3H]muscimol binding was detected when the preparations from the KA-treated and non-treated CS were preincubated with 0.05% Triton X-100, respectively. Scatchard analysis using CS preparations treated with 0.05% Triton X-100 revealed that the affinity of the GABA receptor was increased by treatment with Triton X-100, while the total number of binding sites (Bmax) was unchanged by this treatment. These results suggest that neuronal degeneration produced by KA in vivo and pretreatment of particulate preparations with Triton X-100 in vitro may increase the amount of specifically bound 3H]muscimol to CS preparations by a similar molecular mechanism. |
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Keywords: | [3H]Muscimol binding GABA receptor Kainic acid Chemical denervation Denervation supersensitivity Endogenous inhibitor |
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