[Functional properties of receptors for glutamate and GABA in cultured trigeminal ganglion neurons].
Properties of receptors for glutamate, consisting of kainate, alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), and N-methyl-D-aspartate (NMDA), and gamma-aminobutyric acid (GABA) in the rat trigeminal ganglion (TG) neurons were studied by means of the whole-cell patch-clamp technique. 1. All TG neurons (diameter 20 approximately 40 microns) responded to GABA, but none of them responded to AMPA, NMDA, and glycine. TG neurons responding to kainate were smaller than 25 microns and desensitized by prolonged agonist exposure. 2. On the basis of the dose-response curves, EC50 and Hill coefficient were found to be 13. 7 microM and 1.2 for kainate, while those for GABA were 28.6 microM and 2.0, respectively. 3. Most kainate receptors in the TG neurons showed linear current-voltage (I-V) relations, though some showed inward rectification. The "Instantaneous" I-V relationship for GABA was linear, where as the "steady-state" I-V relationship produced by ramp changes in potential showed outward rectification in some neurons. 4. The number of TG neurons responding to kainate increased until the 8th postnatal day, while all the recorded neurons responded to GABA in postnatal days. The results indicated that there are kainate and GABAA receptors in the TG neurons and suggested that they are composed of various subunits.
Iida
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First Department of Orthodontics, Faculty of Dentistry, Tokyo Medical and Dental University.
D000818:Animals; D009474:Neurons / Q000737:chemistry*; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D018079:Receptors, GABA / Q000032:analysis / Q000502:physiology*; D017470:Receptors, Glutamate / Q000032:analysis / Q000502:physiology*; D018092:Kainic Acid Receptors / Q000032:analysis / Q000502:physiology; D012668:Trigeminal Ganglion / Q000166:cytology*
D018079:Receptors, GABA; D017470:Receptors, Glutamate; D018092:Kainic Acid Receptors