GABA affects the glutamate receptor-chloride channel complex in mechanically isolated and internally perfused Aplysia neurons.
The effects of gamma-aminobutyric acid (GABA) on the glutamate receptor chloride ion (Cl-) channel complex were examined in mechanically isolated and internally perfused Aplysia neurons using a concentration clamp technique. GABA at concentrations of 3 x 10(-6) M or more, concentration dependently delayed the recovery of the glutamate response from desensitization. This effect was independent of the GABA response and Cl- redistribution. Muscimol (10(-4) M) mimicked the effect of GABA. However, this was not the case for baclofen (10(-3) M). In some isolated neurons, GABA at concentrations of more than 10(-4) M clearly induced an additional Cl- current, the current kinetics of which were different from those induced by lower concentrations of GABA. Even in the continued presence of 10(-4) M GABA, which desensitized the fast GABA response, higher concentrations of GABA (3 x 10(-4) M to 10(-2) M) elicited the additional current in a concentration-dependent manner. The presence of 10(-4) M glutamate completely abolished this current, indicating cross-desensitization between the glutamate and slow GABA responses. High concentrations of GABA (3 x 10(-2) M) did not activate the glutamate receptor coupled to the large cation channel. The results suggest that, in Aplysia neurons, the glutamate receptor-Cl- channel complex has some similarities to the GABA receptor-Cl- channel complex.
Oyama
Y
Y
Department of Neurophysiology, Tohoku University School of Medicine, Sendai, Japan.
Ikemoto
Y
Y
Kits
K S
KS
Akaike
N
N
D000818:Animals; D001001:Anura; D001048:Aplysia / Q000378:metabolism*; D001418:Baclofen / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D009118:Muscimol / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010477:Perfusion; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D002712:Chlorides; D007473:Ion Channels; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; D001418:Baclofen