Abstract
1. The inhibtory action of γ-aminobutyric acid (GABA) and of various other ω-amino acids was proved on the crayfish stretch receptor, perfused frog's spinal cord, while α-amino acids related to them were found ineffective.
2. The structure-effect relationship of these inhibitory compounds on the test preparations employed was almost similar: the NH2 and COOH end groups are essential for the blocking action on the discharge of stretch receptor and the spinal reflex activities as well as for preventing the animals from lethal convulsions and blood pressure lowering, while such effects are most potent when these two end groups are separated by three carbon atoms, lengthening and shortening of carbon chain producing a decrease in their effectiveness. With the same chain length, addition of OH group also reduces the effectiveness, but addition of CH3 group seems to exert hardly any effect on it.
3. It was also proved on the crayfish stretch receptor and perfused frog's spinal reflexes that ω-amino acids have anti-acetylcholine, anti-serotonine and antinicotine actions, their potency in these actions being parallel with those of their inhibitory actions by themselves. These antiactions as well as their own inhibitory action were antagonized by atropine, tryptamine, lysergic acid diethylamide, dibenamine, picrotoxin and metrazol, but not by pyribenzamine and strychnine.
4. It was found on the frog's spinal reflexes that vitamine B1 and B12 do not transform the inhibitory action of GABA into an excitatory one, a fact which is not relevant with that reported by Hayashi on dog's generalized seizure.
