Comparative study on barbiturates using isolated single neurons: GABA-mimetic action and augmentatory action on GABA response.
The comparisons among barbiturate derivatives in both GABA-mimetic action and augmentatory effect on GABA response were made. Experiments were performed on single neurones isolated from frog dorsal root ganglia, using a concentration clamp technique which combines a suction pipette technique (internal perfusion and voltage-clamp) with a rapid external solution exchange within 2 ms. Barbiturates employed here were secobarbital, pentobarbital, hexobarbital and phenobarbital. All barbiturates at the concentrations over 1 x 10(-4) M evoked the chloride current (ICl) dose-dependently. In the GABA-mimetic action of barbiturates the potency was in the order of secobarbital greater than pentobarbital greater than hexobarbital greater than phenobarbital. All barbiturates at the concentrations over 1 x 10(-6) M (but up to 1 x 10(-3) M) augmented the GABA-induced ICl. Potency order of barbiturates in augmenting GABA response was the same as that in their GABA-mimetic actions when the concentration was 1 x 10(-4) M or less. However at the concentration of 1 x 10(-3) M the efficacies of secobarbital and pentobarbital in augmenting GABA response were greatly reduced while the other two barbiturates produced further augmentation.
Yakushiji
T
T
Department of Physiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Oyama
Y
Y
Akaike
N
N
D000818:Animals; D001463:Barbiturates / Q000494:pharmacology*; D002712:Chlorides / Q000502:physiology; D005727:Ganglia, Spinal / Q000187:drug effects / Q000502:physiology*; D006591:Hexobarbital / Q000494:pharmacology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D010424:Pentobarbital / Q000494:pharmacology; D011898:Ranidae; D012631:Secobarbital / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D001463:Barbiturates; D002712:Chlorides; D012631:Secobarbital; D005680:gamma-Aminobutyric Acid; D006591:Hexobarbital; D010424:Pentobarbital