Presynaptic modulation Of [3H] GABA release was examined using rat cerebral cortical slices. In vitro addition of muscimol, a GABAA receptor agonist, resulted in a significant suppression of the release of [3H] GABA e...Presynaptic modulation Of [3H] GABA release was examined using rat cerebral cortical slices. In vitro addition of muscimol, a GABAA receptor agonist, resulted in a significant suppression of the release of [3H] GABA evoked evoked by high potassium stimulation in a dose dependent manner, whereas beclofen, a GABAB receptor agonist, had no significant effect on the release. Furthermore, it was found that the suppressive effect of muscimol could be antagonized invariably by bicuculline, a GABAA receptor antagonist. These results suggest that the release of [3H] GABA from rat cerebral conical GABA neurous may be modulated by presynaptic GABAA autoreceptor.展开更多
Objective To investigate the effect of D-AP5 (D-2-amino-5-phosphonopentanoate, a specific NMDA-antagonist) on the increase of intracellular free Ca 2+ concentration ([Ca 2+ ] i) induced by glutamate in isol...Objective To investigate the effect of D-AP5 (D-2-amino-5-phosphonopentanoate, a specific NMDA-antagonist) on the increase of intracellular free Ca 2+ concentration ([Ca 2+ ] i) induced by glutamate in isolated cochlear inner hair cells (IHCs), and to detect the autoreceptors of the IHC membrane. Methods When a laser scanning confocal microscope (LSCM) was used, the exogenous glutamate (Glu)-induced changes in [Ca 2+ ] i of isolated IHCs and OHCs of guinea pig cochlea were observed with fluo-3, a fluorescent probe for [Ca 2+ ] i. After D-AP5 or CNQX (6--cyano--7--nitroguinoxaline--2, 3--dione, a specific AMPA- antagonist) was administrated, the exogenous glutamate (Glu)-induced changes in [Ca 2+ ] i of isolated IHCs were recorded. Results In the presence of a low concentration Glu (3.85?μmol/L), there was an increase of [Ca 2+ ] i in IHCs, whereas there was no change in OHCs. When 50?μmol/L of D-AP5 was administrated in advance, Glu did not induce a corresponding increase in [Ca 2+ ] i in IHCs, and 50?μmol/L of CNQX did not completely block the increase of [Ca 2+ ] i in IHCs. Conclusions These results suggest that the autoreceptors existing in the IHC membrane are mainly of NMDA type, while there are relatively few AMPA receptors. Exogenous Glu is capable of increasing [Ca 2+ ] i in IHCs by acting on the NMDA autoreceptor of IHCs in a positive feedback manner.展开更多
文摘Presynaptic modulation Of [3H] GABA release was examined using rat cerebral cortical slices. In vitro addition of muscimol, a GABAA receptor agonist, resulted in a significant suppression of the release of [3H] GABA evoked evoked by high potassium stimulation in a dose dependent manner, whereas beclofen, a GABAB receptor agonist, had no significant effect on the release. Furthermore, it was found that the suppressive effect of muscimol could be antagonized invariably by bicuculline, a GABAA receptor antagonist. These results suggest that the release of [3H] GABA from rat cerebral conical GABA neurous may be modulated by presynaptic GABAA autoreceptor.
文摘Objective To investigate the effect of D-AP5 (D-2-amino-5-phosphonopentanoate, a specific NMDA-antagonist) on the increase of intracellular free Ca 2+ concentration ([Ca 2+ ] i) induced by glutamate in isolated cochlear inner hair cells (IHCs), and to detect the autoreceptors of the IHC membrane. Methods When a laser scanning confocal microscope (LSCM) was used, the exogenous glutamate (Glu)-induced changes in [Ca 2+ ] i of isolated IHCs and OHCs of guinea pig cochlea were observed with fluo-3, a fluorescent probe for [Ca 2+ ] i. After D-AP5 or CNQX (6--cyano--7--nitroguinoxaline--2, 3--dione, a specific AMPA- antagonist) was administrated, the exogenous glutamate (Glu)-induced changes in [Ca 2+ ] i of isolated IHCs were recorded. Results In the presence of a low concentration Glu (3.85?μmol/L), there was an increase of [Ca 2+ ] i in IHCs, whereas there was no change in OHCs. When 50?μmol/L of D-AP5 was administrated in advance, Glu did not induce a corresponding increase in [Ca 2+ ] i in IHCs, and 50?μmol/L of CNQX did not completely block the increase of [Ca 2+ ] i in IHCs. Conclusions These results suggest that the autoreceptors existing in the IHC membrane are mainly of NMDA type, while there are relatively few AMPA receptors. Exogenous Glu is capable of increasing [Ca 2+ ] i in IHCs by acting on the NMDA autoreceptor of IHCs in a positive feedback manner.
